Active Support Core Extensions¶ ↑
Active Support is the Ruby on Rails component responsible for providing Ruby language extensions, utilities, and other transversal stuff.
It offers a richer bottom-line at the language level, targeted both at the development of Rails applications, and at the development of Ruby on Rails itself.
After reading this guide, you will know:
-
What Core Extensions are.
-
How to load all extensions.
-
How to cherry-pick just the extensions you want.
-
What extensions Active Support provides.
How to Load Core Extensions¶ ↑
Stand-Alone Active Support¶ ↑
In order to have a near-zero default footprint, Active Support does not load anything by default. It is broken in small pieces so that you can load just what you need, and also has some convenience entry points to load related extensions in one shot, even everything.
Thus, after a simple require like:
require 'active_support'
objects do not even respond to blank?
. Let's see how to
load its definition.
Cherry-picking a Definition¶ ↑
The most lightweight way to get blank?
is to cherry-pick the
file that defines it.
For every single method defined as a core extension this guide has a note
that says where such a method is defined. In the case of
blank?
the note reads:
NOTE: Defined in active_support/core_ext/object/blank.rb
.
That means that you can require it like this:
require 'active_support' require 'active_support/core_ext/object/blank'
Active Support has been carefully revised so that cherry-picking a file loads only strictly needed dependencies, if any.
Loading Grouped Core Extensions¶ ↑
The next level is to simply load all extensions to Object
. As
a rule of thumb, extensions to SomeClass
are available in one
shot by loading active_support/core_ext/some_class
.
Thus, to load all extensions to Object
(including
blank?
):
require 'active_support' require 'active_support/core_ext/object'
Loading All Core Extensions¶ ↑
You may prefer just to load all core extensions, there is a file for that:
require 'active_support' require 'active_support/core_ext'
Loading All Active Support¶ ↑
And finally, if you want to have all Active Support available just issue:
require 'active_support/all'
That does not even put the entire Active Support in memory upfront indeed,
some stuff is configured via autoload
, so it is only loaded if
used.
Active Support Within a Ruby on Rails Application¶ ↑
A Ruby on Rails application loads all Active Support unless
config.active_support.bare
is true. In that case, the
application will only load what the framework itself cherry-picks for its
own needs, and can still cherry-pick itself at any granularity level, as
explained in the previous section.
Extensions to All Objects¶ ↑
blank?
and present?
¶ ↑
The following values are considered to be blank in a Rails application:
-
nil
andfalse
, -
strings composed only of whitespace (see note below),
-
empty arrays and hashes, and
-
any other object that responds to
empty?
and is empty.
INFO: The predicate for strings uses the Unicode-aware character class
[:space:]
, so for example U+2029 (paragraph separator) is
considered to be whitespace.
WARNING: Note that numbers are not mentioned. In particular, 0 and 0.0 are not blank.
For example, this method from
ActionController::HttpAuthentication::Token::ControllerMethods
uses blank?
for checking whether a token is present:
def authenticate(controller, &login_procedure) token, options = token_and_options(controller.request) unless token.blank? login_procedure.call(token, options) end end
The method present?
is equivalent to !blank?
.
This example is taken from
ActionDispatch::Http::Cache::Response
:
def set_conditional_cache_control! return if self["Cache-Control"].present? ... end
NOTE: Defined in active_support/core_ext/object/blank.rb
.
presence
¶ ↑
The presence
method returns its receiver if
present?
, and nil
otherwise. It is useful for
idioms like this:
host = config[:host].presence || 'localhost'
NOTE: Defined in active_support/core_ext/object/blank.rb
.
duplicable?
¶ ↑
A few fundamental objects in Ruby are singletons. For example, in the whole life of a program the integer 1 refers always to the same instance:
1.object_id # => 3 Math.cos(0).to_i.object_id # => 3
Hence, there's no way these objects can be duplicated through
dup
or clone
:
true.dup # => TypeError: can't dup TrueClass
Some numbers which are not singletons are not duplicable either:
0.0.clone # => allocator undefined for Float (2**1024).clone # => allocator undefined for Bignum
Active Support provides duplicable?
to programmatically query
an object about this property:
"foo".duplicable? # => true "".duplicable? # => true 0.0.duplicable? # => false false.duplicable? # => false
By definition all objects are duplicable?
except
nil
, false
, true
, symbols, numbers,
class, module, and method objects.
WARNING: Any class can disallow duplication by removing dup
and clone
or raising exceptions from them. Thus only
rescue
can tell whether a given arbitrary object is
duplicable. duplicable?
depends on the hard-coded list above,
but it is much faster than rescue
. Use it only if you know the
hard-coded list is enough in your use case.
NOTE: Defined in active_support/core_ext/object/duplicable.rb
.
deep_dup
¶ ↑
The deep_dup
method returns deep copy of a given object.
Normally, when you dup
an object that contains other objects,
Ruby does not dup
them, so it creates a shallow copy of the
object. If you have an array with a string, for example, it will look like
this:
array = ['string'] duplicate = array.dup duplicate.push 'another-string' # the object was duplicated, so the element was added only to the duplicate array # => ['string'] duplicate # => ['string', 'another-string'] duplicate.first.gsub!('string', 'foo') # first element was not duplicated, it will be changed in both arrays array # => ['foo'] duplicate # => ['foo', 'another-string']
As you can see, after duplicating the Array
instance, we got
another object, therefore we can modify it and the original object will
stay unchanged. This is not true for array's elements, however. Since
dup
does not make deep copy, the string inside the array is
still the same object.
If you need a deep copy of an object, you should use deep_dup
.
Here is an example:
array = ['string'] duplicate = array.deep_dup duplicate.first.gsub!('string', 'foo') array # => ['string'] duplicate # => ['foo']
If the object is not duplicable, deep_dup
will just return it:
number = 1 duplicate = number.deep_dup number.object_id == duplicate.object_id # => true
NOTE: Defined in active_support/core_ext/object/deep_dup.rb
.
try
¶ ↑
When you want to call a method on an object only if it is not
nil
, the simplest way to achieve it is with conditional
statements, adding unnecessary clutter. The alternative is to use
try
. try
is like Object#send
except
that it returns nil
if sent to nil
.
Here is an example:
# without try unless @number.nil? @number.next end # with try @number.try(:next)
Another example is this code from
ActiveRecord::ConnectionAdapters::AbstractAdapter
where
@logger
could be nil
. You can see that the code
uses try
and avoids an unnecessary check.
def log_info(sql, name, ms) if @logger.try(:debug?) name = '%s (%.1fms)' % [name || 'SQL', ms] @logger.debug(format_log_entry(name, sql.squeeze(' '))) end end
try
can also be called without arguments but a block, which
will only be executed if the object is not nil:
@person.try { |p| "#{p.first_name} #{p.last_name}" }
NOTE: Defined in active_support/core_ext/object/try.rb
.
class_eval(*args, &block)
¶ ↑
You can evaluate code in the context of any object's singleton class
using class_eval
:
class Proc def bind(object) block, time = self, Time.current object.class_eval do method_name = "__bind_#{time.to_i}_#{time.usec}" define_method(method_name, &block) method = instance_method(method_name) remove_method(method_name) method end.bind(object) end end
NOTE: Defined in
active_support/core_ext/kernel/singleton_class.rb
.
acts_like?(duck)
¶ ↑
The method acts_like?
provides a way to check whether some
class acts like some other class based on a simple convention: a class that
provides the same interface as String
defines
def acts_like_string? end
which is only a marker, its body or return value are irrelevant. Then, client code can query for duck-type-safeness this way:
some_klass.acts_like?(:string)
Rails has classes that act like Date
or Time
and
follow this contract.
NOTE: Defined in active_support/core_ext/object/acts_like.rb
.
to_param
¶ ↑
All objects in Rails respond to the method to_param
, which is
meant to return something that represents them as values in a query string,
or as URL fragments.
By default to_param
just calls to_s
:
7.to_param # => "7"
The return value of to_param
should not be
escaped:
"Tom & Jerry".to_param # => "Tom & Jerry"
Several classes in Rails overwrite this method.
For example nil
, true
, and false
return themselves. Array#to_param
calls to_param
on the elements and joins the result with “/”:
[0, true, String].to_param # => "0/true/String"
Notably, the Rails routing system calls to_param
on models to
get a value for the :id
placeholder.
ActiveRecord::Base#to_param
returns the id
of a
model, but you can redefine that method in your models. For example, given
class User def to_param "#{id}-#{name.parameterize}" end end
we get:
user_path(@user) # => "/users/357-john-smith"
WARNING. Controllers need to be aware of any redefinition of
to_param
because when a request like that comes in
“357-john-smith” is the value of params[:id]
.
NOTE: Defined in active_support/core_ext/object/to_param.rb
.
to_query
¶ ↑
Except for hashes, given an unescaped key
this method
constructs the part of a query string that would map such key to what
to_param
returns. For example, given
class User def to_param "#{id}-#{name.parameterize}" end end
we get:
current_user.to_query('user') # => user=357-john-smith
This method escapes whatever is needed, both for the key and the value:
account.to_query('company[name]') # => "company%5Bname%5D=Johnson+%26+Johnson"
so its output is ready to be used in a query string.
Arrays return the result of applying to_query
to each element
with key[]
as key, and join the result with “&”:
[3.4, -45.6].to_query('sample') # => "sample%5B%5D=3.4&sample%5B%5D=-45.6"
Hashes also respond to to_query
but with a different
signature. If no argument is passed a call generates a sorted series of
key/value assignments calling to_query(key)
on its values.
Then it joins the result with “&”:
{c: 3, b: 2, a: 1}.to_query # => "a=1&b=2&c=3"
The method Hash#to_query
accepts an optional namespace for the
keys:
{id: 89, name: "John Smith"}.to_query('user') # => "user%5Bid%5D=89&user%5Bname%5D=John+Smith"
NOTE: Defined in active_support/core_ext/object/to_query.rb
.
with_options
¶ ↑
The method with_options
provides a way to factor out common
options in a series of method calls.
Given a default options hash, with_options
yields a proxy
object to a block. Within the block, methods called on the proxy are
forwarded to the receiver with their options merged. For example, you get
rid of the duplication in:
class Account < ActiveRecord::Base has_many :customers, dependent: :destroy has_many :products, dependent: :destroy has_many :invoices, dependent: :destroy has_many :expenses, dependent: :destroy end
this way:
class Account < ActiveRecord::Base with_options dependent: :destroy do |assoc| assoc.has_many :customers assoc.has_many :products assoc.has_many :invoices assoc.has_many :expenses end end
That idiom may convey grouping to the reader as well. For example, say you want to send a newsletter whose language depends on the user. Somewhere in the mailer you could group locale-dependent bits like this:
I18n.with_options locale: user.locale, scope: "newsletter" do |i18n| subject i18n.t :subject body i18n.t :body, user_name: user.name end
TIP: Since with_options
forwards calls to its receiver they
can be nested. Each nesting level will merge inherited defaults in addition
to their own.
NOTE: Defined in
active_support/core_ext/object/with_options.rb
.
JSON support¶ ↑
Active Support provides a better implementation of to_json
than the json
gem ordinarily provides for Ruby objects. This
is because some classes, like Hash
, OrderedHash
and Process::Status
need special handling in order to provide
a proper JSON representation.
NOTE: Defined in active_support/core_ext/object/json.rb
.
Instance Variables¶ ↑
Active Support provides several methods to ease access to instance variables.
instance_values
¶ ↑
The method instance_values
returns a hash that maps instance
variable names without “@” to their corresponding values. Keys are strings:
class C def initialize(x, y) @x, @y = x, y end end C.new(0, 1).instance_values # => {"x" => 0, "y" => 1}
NOTE: Defined in
active_support/core_ext/object/instance_variables.rb
.
instance_variable_names
¶ ↑
The method instance_variable_names
returns an array. Each name
includes the “@” sign.
class C def initialize(x, y) @x, @y = x, y end end C.new(0, 1).instance_variable_names # => ["@x", "@y"]
NOTE: Defined in
active_support/core_ext/object/instance_variables.rb
.
Silencing Warnings, Streams, and Exceptions¶ ↑
The methods silence_warnings
and enable_warnings
change the value of $VERBOSE
accordingly for the duration of
their block, and reset it afterwards:
silence_warnings { Object.const_set "RAILS_DEFAULT_LOGGER", logger }
You can silence any stream while a block runs with
silence_stream
:
silence_stream(STDOUT) do # STDOUT is silent here end
The quietly
method addresses the common use case where you
want to silence STDOUT and STDERR, even in subprocesses:
quietly { system 'bundle install' }
For example, the railties test suite uses that one in a few places to prevent command messages from being echoed intermixed with the progress status.
Silencing exceptions is also possible with suppress
. This
method receives an arbitrary number of exception classes. If an exception
is raised during the execution of the block and is kind_of?
any of the arguments, suppress
captures it and returns
silently. Otherwise the exception is reraised:
# If the user is locked the increment is lost, no big deal. suppress(ActiveRecord::StaleObjectError) do current_user.increment! :visits end
NOTE: Defined in active_support/core_ext/kernel/reporting.rb
.
in?
¶ ↑
The predicate in?
tests if an object is included in another
object. An ArgumentError
exception will be raised if the
argument passed does not respond to include?
.
Examples of in?
:
1.in?([1,2]) # => true "lo".in?("hello") # => true 25.in?(30..50) # => false 1.in?(1) # => ArgumentError
NOTE: Defined in active_support/core_ext/object/inclusion.rb
.
Extensions to Module
¶ ↑
alias_method_chain
¶ ↑
Using plain Ruby you can wrap methods with other methods, that's called alias chaining.
For example, let's say you'd like params to be strings in
functional tests, as they are in real requests, but still want the
convenience of assigning integers and other kind of values. To accomplish
that you could wrap ActionController::TestCase#process
this
way in test/test_helper.rb
:
ActionController::TestCase.class_eval do # save a reference to the original process method alias_method :original_process, :process # now redefine process and delegate to original_process def process(action, params=nil, session=nil, flash=nil, http_method='GET') params = Hash[*params.map {|k, v| [k, v.to_s]}.flatten] original_process(action, params, session, flash, http_method) end end
That's the method get
, post
, etc., delegate
the work to.
That technique has a risk, it could be the case that
:original_process
was taken. To try to avoid collisions people
choose some label that characterizes what the chaining is about:
ActionController::TestCase.class_eval do def process_with_stringified_params(...) params = Hash[*params.map {|k, v| [k, v.to_s]}.flatten] process_without_stringified_params(action, params, session, flash, http_method) end alias_method :process_without_stringified_params, :process alias_method :process, :process_with_stringified_params end
The method alias_method_chain
provides a shortcut for that
pattern:
ActionController::TestCase.class_eval do def process_with_stringified_params(...) params = Hash[*params.map {|k, v| [k, v.to_s]}.flatten] process_without_stringified_params(action, params, session, flash, http_method) end alias_method_chain :process, :stringified_params end
Rails uses alias_method_chain
all over the code base. For
example validations are added to ActiveRecord::Base#save
by
wrapping the method that way in a separate module specialized in
validations.
NOTE: Defined in active_support/core_ext/module/aliasing.rb
.
Attributes¶ ↑
alias_attribute
¶ ↑
Model attributes have a reader, a writer, and a predicate. You can alias a model attribute having the corresponding three methods defined for you in one shot. As in other aliasing methods, the new name is the first argument, and the old name is the second (one mnemonic is that they go in the same order as if you did an assignment):
class User < ActiveRecord::Base # You can refer to the email column as "login". # This can be meaningful for authentication code. alias_attribute :login, :email end
NOTE: Defined in active_support/core_ext/module/aliasing.rb
.
Internal Attributes¶ ↑
When you are defining an attribute in a class that is meant to be subclassed, name collisions are a risk. That's remarkably important for libraries.
Active Support defines the macros attr_internal_reader
,
attr_internal_writer
, and attr_internal_accessor
.
They behave like their Ruby built-in attr_*
counterparts,
except they name the underlying instance variable in a way that makes
collisions less likely.
The macro attr_internal
is a synonym for
attr_internal_accessor
:
# library class ThirdPartyLibrary::Crawler attr_internal :log_level end # client code class MyCrawler < ThirdPartyLibrary::Crawler attr_accessor :log_level end
In the previous example it could be the case that :log_level
does not belong to the public interface of the library and it is only used
for development. The client code, unaware of the potential conflict,
subclasses and defines its own :log_level
. Thanks to
attr_internal
there's no collision.
By default the internal instance variable is named with a leading
underscore, @_log_level
in the example above. That's
configurable via Module.attr_internal_naming_format
though,
you can pass any sprintf
-like format string with a leading
@
and a %s
somewhere, which is where the name
will be placed. The default is "@_%s"
.
Rails uses internal attributes in a few spots, for examples for views:
module ActionView class Base attr_internal :captures attr_internal :request, :layout attr_internal :controller, :template end end
NOTE: Defined in
active_support/core_ext/module/attr_internal.rb
.
Module Attributes¶ ↑
The macros mattr_reader
, mattr_writer
, and
mattr_accessor
are the same as the cattr_*
macros
defined for class. In fact, the cattr_*
macros are just
aliases for the mattr_*
macros. Check Class Attributes.
For example, the dependencies mechanism uses them:
module ActiveSupport module Dependencies mattr_accessor :warnings_on_first_load mattr_accessor :history mattr_accessor :loaded mattr_accessor :mechanism mattr_accessor :load_paths mattr_accessor :load_once_paths mattr_accessor :autoloaded_constants mattr_accessor :explicitly_unloadable_constants mattr_accessor :logger mattr_accessor :log_activity mattr_accessor :constant_watch_stack mattr_accessor :constant_watch_stack_mutex end end
NOTE: Defined in
active_support/core_ext/module/attribute_accessors.rb
.
Parents¶ ↑
parent
¶ ↑
The parent
method on a nested named module returns the module
that contains its corresponding constant:
module X module Y module Z end end end M = X::Y::Z X::Y::Z.parent # => X::Y M.parent # => X::Y
If the module is anonymous or belongs to the top-level, parent
returns Object
.
WARNING: Note that in that case parent_name
returns
nil
.
NOTE: Defined in
active_support/core_ext/module/introspection.rb
.
parent_name
¶ ↑
The parent_name
method on a nested named module returns the
fully-qualified name of the module that contains its corresponding
constant:
module X module Y module Z end end end M = X::Y::Z X::Y::Z.parent_name # => "X::Y" M.parent_name # => "X::Y"
For top-level or anonymous modules parent_name
returns
nil
.
WARNING: Note that in that case parent
returns
Object
.
NOTE: Defined in
active_support/core_ext/module/introspection.rb
.
parents
¶ ↑
The method parents
calls parent
on the receiver
and upwards until Object
is reached. The chain is returned in
an array, from bottom to top:
module X module Y module Z end end end M = X::Y::Z X::Y::Z.parents # => [X::Y, X, Object] M.parents # => [X::Y, X, Object]
NOTE: Defined in
active_support/core_ext/module/introspection.rb
.
Constants¶ ↑
The method local_constants
returns the names of the constants
that have been defined in the receiver module:
module X X1 = 1 X2 = 2 module Y Y1 = :y1 X1 = :overrides_X1_above end end X.local_constants # => [:X1, :X2, :Y] X::Y.local_constants # => [:Y1, :X1]
The names are returned as symbols.
NOTE: Defined in
active_support/core_ext/module/introspection.rb
.
Qualified Constant Names¶ ↑
The standard methods const_defined?
, const_get
,
and const_set
accept bare constant names. Active Support
extends this API to be able to pass relative qualified constant names.
The new methods are qualified_const_defined?
,
qualified_const_get
, and qualified_const_set
.
Their arguments are assumed to be qualified constant names relative to
their receiver:
Object.qualified_const_defined?("Math::PI") # => true Object.qualified_const_get("Math::PI") # => 3.141592653589793 Object.qualified_const_set("Math::Phi", 1.618034) # => 1.618034
Arguments may be bare constant names:
Math.qualified_const_get("E") # => 2.718281828459045
These methods are analogous to their built-in counterparts. In particular,
qualified_constant_defined?
accepts an optional second
argument to be able to say whether you want the predicate to look in the
ancestors. This flag is taken into account for each constant in the
expression while walking down the path.
For example, given
module M X = 1 end module N class C include M end end
qualified_const_defined?
behaves this way:
N.qualified_const_defined?("C::X", false) # => false N.qualified_const_defined?("C::X", true) # => true N.qualified_const_defined?("C::X") # => true
As the last example implies, the second argument defaults to true, as in
const_defined?
.
For coherence with the built-in methods only relative paths are accepted.
Absolute qualified constant names like ::Math::PI
raise
NameError
.
NOTE: Defined in
active_support/core_ext/module/qualified_const.rb
.
Reachable¶ ↑
A named module is reachable if it is stored in its corresponding constant. It means you can reach the module object via the constant.
That is what ordinarily happens, if a module is called “M”, the
M
constant exists and holds it:
module M end M.reachable? # => true
But since constants and modules are indeed kind of decoupled, module objects can become unreachable:
module M end orphan = Object.send(:remove_const, :M) # The module object is orphan now but it still has a name. orphan.name # => "M" # You cannot reach it via the constant M because it does not even exist. orphan.reachable? # => false # Let's define a module called "M" again. module M end # The constant M exists now again, and it stores a module # object called "M", but it is a new instance. orphan.reachable? # => false
NOTE: Defined in active_support/core_ext/module/reachable.rb
.
Anonymous¶ ↑
A module may or may not have a name:
module M end M.name # => "M" N = Module.new N.name # => "N" Module.new.name # => nil
You can check whether a module has a name with the predicate
anonymous?
:
module M end M.anonymous? # => false Module.new.anonymous? # => true
Note that being unreachable does not imply being anonymous:
module M end m = Object.send(:remove_const, :M) m.reachable? # => false m.anonymous? # => false
though an anonymous module is unreachable by definition.
NOTE: Defined in active_support/core_ext/module/anonymous.rb
.
Method Delegation¶ ↑
The macro delegate
offers an easy way to forward methods.
Let's imagine that users in some application have login information in
the User
model but name and other data in a separate
Profile
model:
class User < ActiveRecord::Base has_one :profile end
With that configuration you get a user's name via their profile,
user.profile.name
, but it could be handy to still be able to
access such attribute directly:
class User < ActiveRecord::Base has_one :profile def name profile.name end end
That is what delegate
does for you:
class User < ActiveRecord::Base has_one :profile delegate :name, to: :profile end
It is shorter, and the intention more obvious.
The method must be public in the target.
The delegate
macro accepts several methods:
delegate :name, :age, :address, :twitter, to: :profile
When interpolated into a string, the :to
option should become
an expression that evaluates to the object the method is delegated to.
Typically a string or symbol. Such an expression is evaluated in the
context of the receiver:
# delegates to the Rails constant delegate :logger, to: :Rails # delegates to the receiver's class delegate :table_name, to: :class
WARNING: If the :prefix
option is true
this is
less generic, see below.
By default, if the delegation raises NoMethodError
and the
target is nil
the exception is propagated. You can ask that
nil
is returned instead with the :allow_nil
option:
delegate :name, to: :profile, allow_nil: true
With :allow_nil
the call user.name
returns
nil
if the user has no profile.
The option :prefix
adds a prefix to the name of the generated
method. This may be handy for example to get a better name:
delegate :street, to: :address, prefix: true
The previous example generates address_street
rather than
street
.
WARNING: Since in this case the name of the generated method is composed of
the target object and target method names, the :to
option must
be a method name.
A custom prefix may also be configured:
delegate :size, to: :attachment, prefix: :avatar
In the previous example the macro generates avatar_size
rather
than size
.
NOTE: Defined in active_support/core_ext/module/delegation.rb
Redefining Methods¶ ↑
There are cases where you need to define a method with
define_method
, but don't know whether a method with that
name already exists. If it does, a warning is issued if they are enabled.
No big deal, but not clean either.
The method redefine_method
prevents such a potential warning,
removing the existing method before if needed.
NOTE: Defined in
active_support/core_ext/module/remove_method.rb
Extensions to Class
¶ ↑
Class Attributes¶ ↑
class_attribute
¶ ↑
The method class_attribute
declares one or more inheritable
class attributes that can be overridden at any level down the hierarchy.
class A class_attribute :x end class B < A; end class C < B; end A.x = :a B.x # => :a C.x # => :a B.x = :b A.x # => :a C.x # => :b C.x = :c A.x # => :a B.x # => :b
For example ActionMailer::Base
defines:
class_attribute :default_params self.default_params = { mime_version: "1.0", charset: "UTF-8", content_type: "text/plain", parts_order: [ "text/plain", "text/enriched", "text/html" ] }.freeze
They can also be accessed and overridden at the instance level.
A.x = 1 a1 = A.new a2 = A.new a2.x = 2 a1.x # => 1, comes from A a2.x # => 2, overridden in a2
The generation of the writer instance method can be prevented by setting
the option :instance_writer
to false
.
module ActiveRecord class Base class_attribute :table_name_prefix, instance_writer: false self.table_name_prefix = "" end end
A model may find that option useful as a way to prevent mass-assignment from setting the attribute.
The generation of the reader instance method can be prevented by setting
the option :instance_reader
to false
.
class A class_attribute :x, instance_reader: false end A.new.x = 1 # NoMethodError
For convenience class_attribute
also defines an instance
predicate which is the double negation of what the instance reader returns.
In the examples above it would be called x?
.
When :instance_reader
is false
, the instance
predicate returns a NoMethodError
just like the reader method.
If you do not want the instance predicate, pass instance_predicate:
false
and it will not be defined.
NOTE: Defined in active_support/core_ext/class/attribute.rb
cattr_reader
, cattr_writer
, and cattr_accessor
¶ ↑
The macros cattr_reader
, cattr_writer
, and
cattr_accessor
are analogous to their attr_*
counterparts but for classes. They initialize a class variable to
nil
unless it already exists, and generate the corresponding
class methods to access it:
class MysqlAdapter < AbstractAdapter # Generates class methods to access @@emulate_booleans. cattr_accessor :emulate_booleans self.emulate_booleans = true end
Instance methods are created as well for convenience, they are just proxies
to the class attribute. So, instances can change the class attribute, but
cannot override it as it happens with class_attribute
(see
above). For example given
module ActionView class Base cattr_accessor :field_error_proc @@field_error_proc = Proc.new{ ... } end end
we can access field_error_proc
in views.
Also, you can pass a block to cattr_*
to set up the attribute
with a default value:
class MysqlAdapter < AbstractAdapter # Generates class methods to access @@emulate_booleans with default value of true. cattr_accessor(:emulate_booleans) { true } end
The generation of the reader instance method can be prevented by setting
:instance_reader
to false
and the generation of
the writer instance method can be prevented by setting
:instance_writer
to false
. Generation of both
methods can be prevented by setting :instance_accessor
to
false
. In all cases, the value must be exactly
false
and not any false value.
module A class B # No first_name instance reader is generated. cattr_accessor :first_name, instance_reader: false # No last_name= instance writer is generated. cattr_accessor :last_name, instance_writer: false # No surname instance reader or surname= writer is generated. cattr_accessor :surname, instance_accessor: false end end
A model may find it useful to set :instance_accessor
to
false
as a way to prevent mass-assignment from setting the
attribute.
NOTE: Defined in
active_support/core_ext/module/attribute_accessors.rb
.
Subclasses & Descendants¶ ↑
subclasses
¶ ↑
The subclasses
method returns the subclasses of the receiver:
class C; end C.subclasses # => [] class B < C; end C.subclasses # => [B] class A < B; end C.subclasses # => [B] class D < C; end C.subclasses # => [B, D]
The order in which these classes are returned is unspecified.
NOTE: Defined in active_support/core_ext/class/subclasses.rb
.
descendants
¶ ↑
The descendants
method returns all classes that are
<
than its receiver:
class C; end C.descendants # => [] class B < C; end C.descendants # => [B] class A < B; end C.descendants # => [B, A] class D < C; end C.descendants # => [B, A, D]
The order in which these classes are returned is unspecified.
NOTE: Defined in active_support/core_ext/class/subclasses.rb
.
Extensions to String
¶ ↑
Output Safety¶ ↑
Motivation¶ ↑
Inserting data into HTML templates needs extra care. For example, you
can't just interpolate @review.title
verbatim into an HTML
page. For one thing, if the review title is “Flanagan & Matz rules!”
the output won't be well-formed because an ampersand has to be escaped
as “&”. What's more, depending on the application, that may be
a big security hole because users can inject malicious HTML setting a
hand-crafted review title. Check out the section about cross-site scripting
in the Security guide
for further information about the risks.
Safe Strings¶ ↑
Active Support has the concept of (html) safe strings. A safe string is one that is marked as being insertable into HTML as is. It is trusted, no matter whether it has been escaped or not.
Strings are considered to be unsafe by default:
"".html_safe? # => false
You can obtain a safe string from a given one with the
html_safe
method:
s = "".html_safe s.html_safe? # => true
It is important to understand that html_safe
performs no
escaping whatsoever, it is just an assertion:
s = "<script>...</script>".html_safe s.html_safe? # => true s # => "<script>...</script>"
It is your responsibility to ensure calling html_safe
on a
particular string is fine.
If you append onto a safe string, either in-place with
concat
/<<
, or with +
, the
result is a safe string. Unsafe arguments are escaped:
"".html_safe + "<" # => "<"
Safe arguments are directly appended:
"".html_safe + "<".html_safe # => "<"
These methods should not be used in ordinary views. Unsafe values are automatically escaped:
<%= @review.title %> <%# fine, escaped if needed %>
To insert something verbatim use the raw
helper rather than
calling html_safe
:
<%= raw @cms.current_template %> <%# inserts @cms.current_template as is %>
or, equivalently, use <%==
:
<%== @cms.current_template %> <%# inserts @cms.current_template as is %>
The raw
helper calls html_safe
for you:
def raw(stringish) stringish.to_s.html_safe end
NOTE: Defined in
active_support/core_ext/string/output_safety.rb
.
Transformation¶ ↑
As a rule of thumb, except perhaps for concatenation as explained above,
any method that may change a string gives you an unsafe string. These are
downcase
, gsub
, strip
,
chomp
, underscore
, etc.
In the case of in-place transformations like gsub!
the
receiver itself becomes unsafe.
INFO: The safety bit is lost always, no matter whether the transformation actually changed something.
Conversion and Coercion¶ ↑
Calling to_s
on a safe string returns a safe string, but
coercion with to_str
returns an unsafe string.
Copying¶ ↑
Calling dup
or clone
on safe strings yields safe
strings.
remove
¶ ↑
The method remove
will remove all occurrences of the pattern:
"Hello World".remove(/Hello /) => "World"
There's also the destructive version String#remove!
.
NOTE: Defined in active_support/core_ext/string/filters.rb
.
squish
¶ ↑
The method squish
strips leading and trailing whitespace, and
substitutes runs of whitespace with a single space each:
" \n foo\n\r \t bar \n".squish # => "foo bar"
There's also the destructive version String#squish!
.
Note that it handles both ASCII and Unicode whitespace.
NOTE: Defined in active_support/core_ext/string/filters.rb
.
truncate
¶ ↑
The method truncate
returns a copy of its receiver truncated
after a given length
:
"Oh dear! Oh dear! I shall be late!".truncate(20) # => "Oh dear! Oh dear!..."
Ellipsis can be customized with the :omission
option:
"Oh dear! Oh dear! I shall be late!".truncate(20, omission: '…') # => "Oh dear! Oh …"
Note in particular that truncation takes into account the length of the omission string.
Pass a :separator
to truncate the string at a natural break:
"Oh dear! Oh dear! I shall be late!".truncate(18) # => "Oh dear! Oh dea..." "Oh dear! Oh dear! I shall be late!".truncate(18, separator: ' ') # => "Oh dear! Oh..."
The option :separator
can be a regexp:
"Oh dear! Oh dear! I shall be late!".truncate(18, separator: /\s/) # => "Oh dear! Oh..."
In above examples “dear” gets cut first, but then :separator
prevents it.
NOTE: Defined in active_support/core_ext/string/filters.rb
.
truncate_words
¶ ↑
The method truncate_words
returns a copy of its receiver
truncated after a given number of words:
"Oh dear! Oh dear! I shall be late!".truncate_words(4) # => "Oh dear! Oh dear!..."
Ellipsis can be customized with the :omission
option:
"Oh dear! Oh dear! I shall be late!".truncate_words(4, omission: '…') # => "Oh dear! Oh dear!…"
Pass a :separator
to truncate the string at a natural break:
"Oh dear! Oh dear! I shall be late!".truncate_words(3, separator: '!') # => "Oh dear! Oh dear! I shall be late..."
The option :separator
can be a regexp:
"Oh dear! Oh dear! I shall be late!".truncate_words(4, separator: /\s/) # => "Oh dear! Oh dear!..."
NOTE: Defined in active_support/core_ext/string/filters.rb
.
inquiry
¶ ↑
The inquiry
method converts a string into a
StringInquirer
object making equality checks prettier.
"production".inquiry.production? # => true "active".inquiry.inactive? # => false
starts_with?
and ends_with?
¶ ↑
Active Support defines 3rd person aliases of
String#start_with?
and String#end_with?
:
"foo".starts_with?("f") # => true "foo".ends_with?("o") # => true
NOTE: Defined in
active_support/core_ext/string/starts_ends_with.rb
.
strip_heredoc
¶ ↑
The method strip_heredoc
strips indentation in heredocs.
For example in
if options[:usage] puts " This command does such and such. Supported options are: -h This message ... ".strip_heredoc end
the user would see the usage message aligned against the left margin.
Technically, it looks for the least indented line in the whole string, and removes that amount of leading whitespace.
NOTE: Defined in active_support/core_ext/string/strip.rb
.
indent
¶ ↑
Indents the lines in the receiver:
"def some_method some_code end ".indent(2) # => def some_method some_code end
The second argument, indent_string
, specifies which indent
string to use. The default is nil
, which tells the method to
make an educated guess peeking at the first indented line, and fallback to
a space if there is none.
" foo".indent(2) # => " foo" "foo\n\t\tbar".indent(2) # => "\t\tfoo\n\t\t\t\tbar" "foo".indent(2, "\t") # => "\t\tfoo"
While indent_string
is typically one space or tab, it may be
any string.
The third argument, indent_empty_lines
, is a flag that says
whether empty lines should be indented. Default is false.
"foo\n\nbar".indent(2) # => " foo\n\n bar" "foo\n\nbar".indent(2, nil, true) # => " foo\n \n bar"
The indent!
method performs indentation in-place.
NOTE: Defined in active_support/core_ext/string/indent.rb
.
Access¶ ↑
at(position)
¶ ↑
Returns the character of the string at position position
:
"hello".at(0) # => "h" "hello".at(4) # => "o" "hello".at(-1) # => "o" "hello".at(10) # => nil
NOTE: Defined in active_support/core_ext/string/access.rb
.
from(position)
¶ ↑
Returns the substring of the string starting at position
position
:
"hello".from(0) # => "hello" "hello".from(2) # => "llo" "hello".from(-2) # => "lo" "hello".from(10) # => "" if < 1.9, nil in 1.9
NOTE: Defined in active_support/core_ext/string/access.rb
.
to(position)
¶ ↑
Returns the substring of the string up to position position
:
"hello".to(0) # => "h" "hello".to(2) # => "hel" "hello".to(-2) # => "hell" "hello".to(10) # => "hello"
NOTE: Defined in active_support/core_ext/string/access.rb
.
first(limit = 1)
¶ ↑
The call str.first(n)
is equivalent to
str.to(n-1)
if n
> 0, and returns an empty
string for n
== 0.
NOTE: Defined in active_support/core_ext/string/access.rb
.
last(limit = 1)
¶ ↑
The call str.last(n)
is equivalent to
str.from(-n)
if n
> 0, and returns an empty
string for n
== 0.
NOTE: Defined in active_support/core_ext/string/access.rb
.
Inflections¶ ↑
pluralize
¶ ↑
The method pluralize
returns the plural of its receiver:
"table".pluralize # => "tables" "ruby".pluralize # => "rubies" "equipment".pluralize # => "equipment"
As the previous example shows, Active Support knows some irregular plurals
and uncountable nouns. Built-in rules can be extended in
config/initializers/inflections.rb
. That file is generated by
the rails
command and has instructions in comments.
pluralize
can also take an optional count
parameter. If count == 1
the singular form will be returned.
For any other value of count
the plural form will be returned:
"dude".pluralize(0) # => "dudes" "dude".pluralize(1) # => "dude" "dude".pluralize(2) # => "dudes"
Active Record uses this method to compute the default table name that corresponds to a model:
# active_record/model_schema.rb def undecorated_table_name(class_name = base_class.name) table_name = class_name.to_s.demodulize.underscore pluralize_table_names ? table_name.pluralize : table_name end
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
singularize
¶ ↑
The inverse of pluralize
:
"tables".singularize # => "table" "rubies".singularize # => "ruby" "equipment".singularize # => "equipment"
Associations compute the name of the corresponding default associated class using this method:
# active_record/reflection.rb def derive_class_name class_name = name.to_s.camelize class_name = class_name.singularize if collection? class_name end
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
camelize
¶ ↑
The method camelize
returns its receiver in camel case:
"product".camelize # => "Product" "admin_user".camelize # => "AdminUser"
As a rule of thumb you can think of this method as the one that transforms paths into Ruby class or module names, where slashes separate namespaces:
"backoffice/session".camelize # => "Backoffice::Session"
For example, Action Pack uses this method to load the class that provides a certain session store:
# action_controller/metal/session_management.rb def session_store=(store) @@session_store = store.is_a?(Symbol) ? ActionDispatch::Session.const_get(store.to_s.camelize) : store end
camelize
accepts an optional argument, it can be
:upper
(default), or :lower
. With the latter the
first letter becomes lowercase:
"visual_effect".camelize(:lower) # => "visualEffect"
That may be handy to compute method names in a language that follows that convention, for example JavaScript.
INFO: As a rule of thumb you can think of camelize
as the
inverse of underscore
, though there are cases where that does
not hold: "SSLError".underscore.camelize
gives back
"SslError"
. To support cases such as this, Active
Support allows you to specify acronyms in
config/initializers/inflections.rb
:
ActiveSupport::Inflector.inflections do |inflect| inflect.acronym 'SSL' end "SSLError".underscore.camelize # => "SSLError"
camelize
is aliased to camelcase
.
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
underscore
¶ ↑
The method underscore
goes the other way around, from camel
case to paths:
"Product".underscore # => "product" "AdminUser".underscore # => "admin_user"
Also converts “::” back to “/”:
"Backoffice::Session".underscore # => "backoffice/session"
and understands strings that start with lowercase:
"visualEffect".underscore # => "visual_effect"
underscore
accepts no argument though.
Rails class and module autoloading uses underscore
to infer
the relative path without extension of a file that would define a given
missing constant:
# active_support/dependencies.rb def load_missing_constant(from_mod, const_name) ... qualified_name = qualified_name_for from_mod, const_name path_suffix = qualified_name.underscore ... end
INFO: As a rule of thumb you can think of underscore
as the
inverse of camelize
, though there are cases where that does
not hold. For example,
"SSLError".underscore.camelize
gives back
"SslError"
.
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
titleize
¶ ↑
The method titleize
capitalizes the words in the receiver:
"alice in wonderland".titleize # => "Alice In Wonderland" "fermat's enigma".titleize # => "Fermat's Enigma"
titleize
is aliased to titlecase
.
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
dasherize
¶ ↑
The method dasherize
replaces the underscores in the receiver
with dashes:
"name".dasherize # => "name" "contact_data".dasherize # => "contact-data"
The XML serializer of models uses this method to dasherize node names:
# active_model/serializers/xml.rb def reformat_name(name) name = name.camelize if camelize? dasherize? ? name.dasherize : name end
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
demodulize
¶ ↑
Given a string with a qualified constant name, demodulize
returns the very constant name, that is, the rightmost part of it:
"Product".demodulize # => "Product" "Backoffice::UsersController".demodulize # => "UsersController" "Admin::Hotel::ReservationUtils".demodulize # => "ReservationUtils" "::Inflections".demodulize # => "Inflections" "".demodulize # => ""
Active Record for example uses this method to compute the name of a counter cache column:
# active_record/reflection.rb def counter_cache_column if options[:counter_cache] == true "#{active_record.name.demodulize.underscore.pluralize}_count" elsif options[:counter_cache] options[:counter_cache] end end
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
deconstantize
¶ ↑
Given a string with a qualified constant reference expression,
deconstantize
removes the rightmost segment, generally leaving
the name of the constant's container:
"Product".deconstantize # => "" "Backoffice::UsersController".deconstantize # => "Backoffice" "Admin::Hotel::ReservationUtils".deconstantize # => "Admin::Hotel"
Active Support for example uses this method in
Module#qualified_const_set
:
def qualified_const_set(path, value) QualifiedConstUtils.raise_if_absolute(path) const_name = path.demodulize mod_name = path.deconstantize mod = mod_name.empty? ? self : qualified_const_get(mod_name) mod.const_set(const_name, value) end
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
parameterize
¶ ↑
The method parameterize
normalizes its receiver in a way that
can be used in pretty URLs.
"John Smith".parameterize # => "john-smith" "Kurt Gödel".parameterize # => "kurt-godel"
In fact, the result string is wrapped in an instance of
ActiveSupport::Multibyte::Chars
.
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
tableize
¶ ↑
The method tableize
is underscore
followed by
pluralize
.
"Person".tableize # => "people" "Invoice".tableize # => "invoices" "InvoiceLine".tableize # => "invoice_lines"
As a rule of thumb, tableize
returns the table name that
corresponds to a given model for simple cases. The actual implementation in
Active Record is not straight tableize
indeed, because it also
demodulizes the class name and checks a few options that may affect the
returned string.
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
classify
¶ ↑
The method classify
is the inverse of tableize
.
It gives you the class name corresponding to a table name:
"people".classify # => "Person" "invoices".classify # => "Invoice" "invoice_lines".classify # => "InvoiceLine"
The method understands qualified table names:
"highrise_production.companies".classify # => "Company"
Note that classify
returns a class name as a string. You can
get the actual class object invoking constantize
on it,
explained next.
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
constantize
¶ ↑
The method constantize
resolves the constant reference
expression in its receiver:
"Fixnum".constantize # => Fixnum module M X = 1 end "M::X".constantize # => 1
If the string evaluates to no known constant, or its content is not even a
valid constant name, constantize
raises
NameError
.
Constant name resolution by constantize
starts always at the
top-level Object
even if there is no leading “::”.
X = :in_Object module M X = :in_M X # => :in_M "::X".constantize # => :in_Object "X".constantize # => :in_Object (!) end
So, it is in general not equivalent to what Ruby would do in the same spot, had a real constant be evaluated.
Mailer test cases obtain the mailer being tested from the name of the test
class using constantize
:
# action_mailer/test_case.rb def determine_default_mailer(name) name.sub(/Test$/, '').constantize rescue NameError => e raise NonInferrableMailerError.new(name) end
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
humanize
¶ ↑
The method humanize
tweaks an attribute name for display to
end users.
Specifically performs these transformations:
-
Applies human inflection rules to the argument.
-
Deletes leading underscores, if any.
-
Removes a “_id” suffix if present.
-
Replaces underscores with spaces, if any.
-
Downcases all words except acronyms.
-
Capitalizes the first word.
The capitalization of the first word can be turned off by setting the
:capitalize
option to false (default is true).
"name".humanize # => "Name" "author_id".humanize # => "Author" "author_id".humanize(capitalize: false) # => "author" "comments_count".humanize # => "Comments count" "_id".humanize # => "Id"
If “SSL” was defined to be an acronym:
'ssl_error'.humanize # => "SSL error"
The helper method full_messages
uses humanize
as
a fallback to include attribute names:
def full_messages map { |attribute, message| full_message(attribute, message) } end def full_message ... attr_name = attribute.to_s.tr('.', '_').humanize attr_name = @base.class.human_attribute_name(attribute, default: attr_name) ... end
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
foreign_key
¶ ↑
The method foreign_key
gives a foreign key column name from a
class name. To do so it demodulizes, underscores, and adds “_id”:
"User".foreign_key # => "user_id" "InvoiceLine".foreign_key # => "invoice_line_id" "Admin::Session".foreign_key # => "session_id"
Pass a false argument if you do not want the underscore in “_id”:
"User".foreign_key(false) # => "userid"
Associations use this method to infer foreign keys, for example
has_one
and has_many
do this:
# active_record/associations.rb foreign_key = options[:foreign_key] || reflection.active_record.name.foreign_key
NOTE: Defined in
active_support/core_ext/string/inflections.rb
.
Conversions¶ ↑
to_date
, to_time
, to_datetime
¶ ↑
The methods to_date
, to_time
, and
to_datetime
are basically convenience wrappers around
Date._parse
:
"2010-07-27".to_date # => Tue, 27 Jul 2010 "2010-07-27 23:37:00".to_time # => Tue Jul 27 23:37:00 UTC 2010 "2010-07-27 23:37:00".to_datetime # => Tue, 27 Jul 2010 23:37:00 +0000
to_time
receives an optional argument :utc
or
:local
, to indicate which time zone you want the time in:
"2010-07-27 23:42:00".to_time(:utc) # => Tue Jul 27 23:42:00 UTC 2010 "2010-07-27 23:42:00".to_time(:local) # => Tue Jul 27 23:42:00 +0200 2010
Default is :utc
.
Please refer to the documentation of Date._parse
for further
details.
INFO: The three of them return nil
for blank receivers.
NOTE: Defined in
active_support/core_ext/string/conversions.rb
.
Extensions to Numeric
¶ ↑
Bytes¶ ↑
All numbers respond to these methods:
bytes kilobytes megabytes gigabytes terabytes petabytes exabytes
They return the corresponding amount of bytes, using a conversion factor of 1024:
2.kilobytes # => 2048 3.megabytes # => 3145728 3.5.gigabytes # =><PHONE_NUMBER> -4.exabytes # => -4611686018427387904
Singular forms are aliased so you are able to say:
1.megabyte # => 1048576
NOTE: Defined in active_support/core_ext/numeric/bytes.rb
.
Time¶ ↑
Enables the use of time calculations and declarations, like
45.minutes + 2.hours + 4.years
.
These methods use Time#advance for precise date calculations when using from_now, ago, etc. as well as adding or subtracting their results from a Time object. For example:
# equivalent to Time.current.advance(months: 1) 1.month.from_now # equivalent to Time.current.advance(years: 2) 2.years.from_now # equivalent to Time.current.advance(months: 4, years: 5) (4.months + 5.years).from_now
Formatting¶ ↑
Enables the formatting of numbers in a variety of ways.
Produce a string representation of a number as a telephone number:
5551234.to_s(:phone) # => 555-1234<PHONE_NUMBER>.to_s(:phone) # =><PHONE_NUMBER><PHONE_NUMBER>.to_s(:phone, area_code: true) # =><PHONE_NUMBER><PHONE_NUMBER>.to_s(:phone, delimiter: " ") # =><PHONE_NUMBER><PHONE_NUMBER>.to_s(:phone, area_code: true, extension: 555) # =><PHONE_NUMBER> x<PHONE_NUMBER>234.to_s(:phone, country_code: 1) # => +1-123-555-1234
Produce a string representation of a number as currency:
1234567890.50.to_s(:currency) # => $1,234,567,890.50<PHONE_NUMBER>.506.to_s(:currency) # => $1,234,567,890.51<PHONE_NUMBER>.506.to_s(:currency, precision: 3) # => $1,234,567,890.506
Produce a string representation of a number as a percentage:
100.to_s(:percentage) # => 100.000% 100.to_s(:percentage, precision: 0) # => 100% 1000.to_s(:percentage, delimiter: '.', separator: ',') # => 1.000,000%<PHONE_NUMBER>3423.to_s(:percentage, precision: 5) # => 302.24399%
Produce a string representation of a number in delimited form:
12345678.to_s(:delimited) # => 12,345,678 12345678.05.to_s(:delimited) # => 12,345,678.05 12345678.to_s(:delimited, delimiter: ".") # => 12.345.678 12345678.to_s(:delimited, delimiter: ",") # => 12,345,678 12345678.05.to_s(:delimited, separator: " ") # => 12,345,678 05
Produce a string representation of a number rounded to a precision:
111.2345.to_s(:rounded) # => 111.235 111.2345.to_s(:rounded, precision: 2) # => 111.23 13.to_s(:rounded, precision: 5) # => 13.00000 389.32314.to_s(:rounded, precision: 0) # =><PHONE_NUMBER>.to_s(:rounded, significant: true) # => 111
Produce a string representation of a number as a human-readable number of bytes:
123.to_s(:human_size) # => 123 Bytes 1234.to_s(:human_size) # => 1.21 KB 12345.to_s(:human_size) # => 12.1 KB 1234567.to_s(:human_size) # => 1.18 MB<PHONE_NUMBER>.to_s(:human_size) # => 1.15 GB<PHONE_NUMBER>123.to_s(:human_size) # => 1.12 TB
Produce a string representation of a number in human-readable words:
123.to_s(:human) # => "123" 1234.to_s(:human) # => "1.23 Thousand" 12345.to_s(:human) # => "12.3 Thousand" 1234567.to_s(:human) # => "1.23 Million"<PHONE_NUMBER>.to_s(:human) # => "1.23 Billion"<PHONE_NUMBER>123.to_s(:human) # => "1.23 Trillion"<PHONE_NUMBER>123456.to_s(:human) # => "1.23 Quadrillion"
NOTE: Defined in
active_support/core_ext/numeric/conversions.rb
.
Extensions to Integer
¶ ↑
multiple_of?
¶ ↑
The method multiple_of?
tests whether an integer is multiple
of the argument:
2.multiple_of?(1) # => true 1.multiple_of?(2) # => false
NOTE: Defined in active_support/core_ext/integer/multiple.rb
.
ordinal
¶ ↑
The method ordinal
returns the ordinal suffix string
corresponding to the receiver integer:
1.ordinal # => "st" 2.ordinal # => "nd" 53.ordinal # => "rd" 2009.ordinal # => "th" -21.ordinal # => "st" -134.ordinal # => "th"
NOTE: Defined in
active_support/core_ext/integer/inflections.rb
.
ordinalize
¶ ↑
The method ordinalize
returns the ordinal string corresponding
to the receiver integer. In comparison, note that the ordinal
method returns only the suffix string.
1.ordinalize # => "1st" 2.ordinalize # => "2nd" 53.ordinalize # => "53rd" 2009.ordinalize # => "2009th" -21.ordinalize # => "-21st" -134.ordinalize # => "-134th"
NOTE: Defined in
active_support/core_ext/integer/inflections.rb
.
Extensions to BigDecimal
¶ ↑
to_s
¶ ↑
The method to_s
is aliased to to_formatted_s
.
This provides a convenient way to display a BigDecimal value in
floating-point notation:
BigDecimal.new(5.00, 6).to_s # => "5.0"
to_formatted_s
¶ ↑
Te method to_formatted_s
provides a default specifier of “F”.
This means that a simple call to to_formatted_s
or
to_s
will result in floating point representation instead of
engineering notation:
BigDecimal.new(5.00, 6).to_formatted_s # => "5.0"
and that symbol specifiers are also supported:
BigDecimal.new(5.00, 6).to_formatted_s(:db) # => "5.0"
Engineering notation is still supported:
BigDecimal.new(5.00, 6).to_formatted_s("e") # => "0.5E1"
Extensions to Enumerable
¶ ↑
sum
¶ ↑
The method sum
adds the elements of an enumerable:
[1, 2, 3].sum # => 6 (1..100).sum # => 5050
Addition only assumes the elements respond to +
:
[[1, 2], [2, 3], [3, 4]].sum # => [1, 2, 2, 3, 3, 4] %w(foo bar baz).sum # => "foobarbaz" {a: 1, b: 2, c: 3}.sum # => [:b, 2, :c, 3, :a, 1]
The sum of an empty collection is zero by default, but this is customizable:
[].sum # => 0 [].sum(1) # => 1
If a block is given, sum
becomes an iterator that yields the
elements of the collection and sums the returned values:
(1..5).sum {|n| n * 2 } # => 30 [2, 4, 6, 8, 10].sum # => 30
The sum of an empty receiver can be customized in this form as well:
[].sum(1) {|n| n**3} # => 1
NOTE: Defined in active_support/core_ext/enumerable.rb
.
index_by
¶ ↑
The method index_by
generates a hash with the elements of an
enumerable indexed by some key.
It iterates through the collection and passes each element to a block. The element will be keyed by the value returned by the block:
invoices.index_by(&:number) # => {'2009-032' => <Invoice ...>, '2009-008' => <Invoice ...>, ...}
WARNING. Keys should normally be unique. If the block returns the same value for different elements no collection is built for that key. The last item will win.
NOTE: Defined in active_support/core_ext/enumerable.rb
.
many?
¶ ↑
The method many?
is shorthand for collection.size >
1
:
<% if pages.many? %> <%= pagination_links %> <% end %>
If an optional block is given, many?
only takes into account
those elements that return true:
@see_more = videos.many? {|video| video.category == params[:category]}
NOTE: Defined in active_support/core_ext/enumerable.rb
.
exclude?
¶ ↑
The predicate exclude?
tests whether a given object does
not belong to the collection. It is the negation of the
built-in include?
:
to_visit << node if visited.exclude?(node)
NOTE: Defined in active_support/core_ext/enumerable.rb
.
Extensions to Array
¶ ↑
Accessing¶ ↑
Active Support augments the API of arrays to ease certain ways of accessing
them. For example, to
returns the subarray of elements up to
the one at the passed index:
%w(a b c d).to(2) # => %w(a b c) [].to(7) # => []
Similarly, from
returns the tail from the element at the
passed index to the end. If the index is greater than the length of the
array, it returns an empty array.
%w(a b c d).from(2) # => %w(c d) %w(a b c d).from(10) # => [] [].from(0) # => []
The methods second
, third
, fourth
,
and fifth
return the corresponding element (first
is built-in). Thanks to social wisdom and positive constructiveness all
around, forty_two
is also available.
%w(a b c d).third # => c %w(a b c d).fifth # => nil
NOTE: Defined in active_support/core_ext/array/access.rb
.
Adding Elements¶ ↑
prepend
¶ ↑
This method is an alias of Array#unshift
.
%w(a b c d).prepend('e') # => %w(e a b c d) [].prepend(10) # => [10]
NOTE: Defined in
active_support/core_ext/array/prepend_and_append.rb
.
append
¶ ↑
This method is an alias of Array#<<
.
%w(a b c d).append('e') # => %w(a b c d e) [].append([1,2]) # => [[1,2]]
NOTE: Defined in
active_support/core_ext/array/prepend_and_append.rb
.
Options Extraction¶ ↑
When the last argument in a method call is a hash, except perhaps for a
&block
argument, Ruby allows you to omit the brackets:
User.exists?(email: params[:email])
That syntactic sugar is used a lot in Rails to avoid positional arguments where there would be too many, offering instead interfaces that emulate named parameters. In particular it is very idiomatic to use a trailing hash for options.
If a method expects a variable number of arguments and uses *
in its declaration, however, such an options hash ends up being an item of
the array of arguments, where it loses its role.
In those cases, you may give an options hash a distinguished treatment with
extract_options!
. This method checks the type of the last item
of an array. If it is a hash it pops it and returns it, otherwise it
returns an empty hash.
Let's see for example the definition of the caches_action
controller macro:
def caches_action(*actions) return unless cache_configured? options = actions.extract_options! ... end
This method receives an arbitrary number of action names, and an optional
hash of options as last argument. With the call to
extract_options!
you obtain the options hash and remove it
from actions
in a simple and explicit way.
NOTE: Defined in
active_support/core_ext/array/extract_options.rb
.
Conversions¶ ↑
to_sentence
¶ ↑
The method to_sentence
turns an array into a string containing
a sentence that enumerates its items:
%w().to_sentence # => "" %w(Earth).to_sentence # => "Earth" %w(Earth Wind).to_sentence # => "Earth and Wind" %w(Earth Wind Fire).to_sentence # => "Earth, Wind, and Fire"
This method accepts three options:
-
:two_words_connector
: What is used for arrays of length 2. Default is “ and ”. -
:words_connector
: What is used to join the elements of arrays with 3 or more elements, except for the last two. Default is “, ”. -
:last_word_connector
: What is used to join the last items of an array with 3 or more elements. Default is “, and ”.
The defaults for these options can be localized, their keys are:
| Option | I18n key | | ———————- | ———————————– | |
:two_words_connector
|
support.array.two_words_connector
| |
:words_connector
| support.array.words_connector
| | :last_word_connector
|
support.array.last_word_connector
|
NOTE: Defined in active_support/core_ext/array/conversions.rb
.
to_formatted_s
¶ ↑
The method to_formatted_s
acts like to_s
by
default.
If the array contains items that respond to id
, however, the
symbol :db
may be passed as argument. That's typically
used with collections of Active Record objects. Returned strings are:
[].to_formatted_s(:db) # => "null" [user].to_formatted_s(:db) # => "8456" invoice.lines.to_formatted_s(:db) # => "23,567,556,12"
Integers in the example above are supposed to come from the respective
calls to id
.
NOTE: Defined in active_support/core_ext/array/conversions.rb
.
to_xml
¶ ↑
The method to_xml
returns a string containing an XML
representation of its receiver:
Contributor.limit(2).order(:rank).to_xml # => # <?xml version="1.0" encoding="UTF-8"?> # <contributors type="array"> # <contributor> # <id type="integer">4356</id> # <name>Jeremy Kemper</name> # <rank type="integer">1</rank> # <url-id>jeremy-kemper</url-id> # </contributor> # <contributor> # <id type="integer">4404</id> # <name>David Heinemeier Hansson</name> # <rank type="integer">2</rank> # <url-id>david-heinemeier-hansson</url-id> # </contributor> # </contributors>
To do so it sends to_xml
to every item in turn, and collects
the results under a root node. All items must respond to
to_xml
, an exception is raised otherwise.
By default, the name of the root element is the underscorized and
dasherized plural of the name of the class of the first item, provided the
rest of elements belong to that type (checked with is_a?
) and
they are not hashes. In the example above that's “contributors”.
If there's any element that does not belong to the type of the first one the root node becomes “objects”:
[Contributor.first, Commit.first].to_xml # => # <?xml version="1.0" encoding="UTF-8"?> # <objects type="array"> # <object> # <id type="integer">4583</id> # <name>Aaron Batalion</name> # <rank type="integer">53</rank> # <url-id>aaron-batalion</url-id> # </object> # <object> # <author>Joshua Peek</author> # <authored-timestamp type="datetime">2009-09-02T16:44:36Z</authored-timestamp> # <branch>origin/master</branch> # <committed-timestamp type="datetime">2009-09-02T16:44:36Z</committed-timestamp> # <committer>Joshua Peek</committer> # <git-show nil="true"></git-show> # <id type="integer">190316</id> # <imported-from-svn type="boolean">false</imported-from-svn> # <message>Kill AMo observing wrap_with_notifications since ARes was only using it</message> # <sha1>723a47bfb3708f968821bc969a9a3fc873a3ed58</sha1> # </object> # </objects>
If the receiver is an array of hashes the root element is by default also “objects”:
[{a: 1, b: 2}, {c: 3}].to_xml # => # <?xml version="1.0" encoding="UTF-8"?> # <objects type="array"> # <object> # <b type="integer">2</b> # <a type="integer">1</a> # </object> # <object> # <c type="integer">3</c> # </object> # </objects>
WARNING. If the collection is empty the root element is by default
“nil-classes”. That's a gotcha, for example the root element of the
list of contributors above would not be “contributors” if the collection
was empty, but “nil-classes”. You may use the :root
option to
ensure a consistent root element.
The name of children nodes is by default the name of the root node
singularized. In the examples above we've seen “contributor” and
“object”. The option :children
allows you to set these node
names.
The default XML builder is a fresh instance of
Builder::XmlMarkup
. You can configure your own builder via the
:builder
option. The method also accepts options like
:dasherize
and friends, they are forwarded to the builder:
Contributor.limit(2).order(:rank).to_xml(skip_types: true) # => # <?xml version="1.0" encoding="UTF-8"?> # <contributors> # <contributor> # <id>4356</id> # <name>Jeremy Kemper</name> # <rank>1</rank> # <url-id>jeremy-kemper</url-id> # </contributor> # <contributor> # <id>4404</id> # <name>David Heinemeier Hansson</name> # <rank>2</rank> # <url-id>david-heinemeier-hansson</url-id> # </contributor> # </contributors>
NOTE: Defined in active_support/core_ext/array/conversions.rb
.
Wrapping¶ ↑
The method Array.wrap
wraps its argument in an array unless it
is already an array (or array-like).
Specifically:
-
If the argument is
nil
an empty list is returned. -
Otherwise, if the argument responds to
to_ary
it is invoked, and if the value ofto_ary
is notnil
, it is returned. -
Otherwise, an array with the argument as its single element is returned.
Array.wrap(nil) # => [] Array.wrap([1, 2, 3]) # => [1, 2, 3] Array.wrap(0) # => [0]
This method is similar in purpose to Kernel#Array
, but there
are some differences:
-
If the argument responds to
to_ary
the method is invoked.Kernel#Array
moves on to tryto_a
if the returned value isnil
, butArray.wrap
returnsnil
right away. -
If the returned value from
to_ary
is neithernil
nor anArray
object,Kernel#Array
raises an exception, whileArray.wrap
does not, it just returns the value. -
It does not call
to_a
on the argument, though special-casesnil
to return an empty array.
The last point is particularly worth comparing for some enumerables:
Array.wrap(foo: :bar) # => [{:foo=>:bar}] Array(foo: :bar) # => [[:foo, :bar]]
There's also a related idiom that uses the splat operator:
[*object]
which in Ruby 1.8 returns [nil]
for nil
, and
calls to Array(object)
otherwise. (Please if you know the
exact behavior in 1.9 contact fxn.)
Thus, in this case the behavior is different for nil
, and the
differences with Kernel#Array
explained above apply to the
rest of object
s.
NOTE: Defined in active_support/core_ext/array/wrap.rb
.
Duplicating¶ ↑
The method Array.deep_dup
duplicates itself and all objects
inside recursively with Active Support method Object#deep_dup
.
It works like Array#map
with sending deep_dup
method to each object inside.
array = [1, [2, 3]] dup = array.deep_dup dup[1][2] = 4 array[1][2] == nil # => true
NOTE: Defined in active_support/core_ext/object/deep_dup.rb
.
Grouping¶ ↑
in_groups_of(number, fill_with = nil)
¶ ↑
The method in_groups_of
splits an array into consecutive
groups of a certain size. It returns an array with the groups:
[1, 2, 3].in_groups_of(2) # => [[1, 2], [3, nil]]
or yields them in turn if a block is passed:
<% sample.in_groups_of(3) do |a, b, c| %> <tr> <td><%= a %></td> <td><%= b %></td> <td><%= c %></td> </tr> <% end %>
The first example shows in_groups_of
fills the last group with
as many nil
elements as needed to have the requested size. You
can change this padding value using the second optional argument:
[1, 2, 3].in_groups_of(2, 0) # => [[1, 2], [3, 0]]
And you can tell the method not to fill the last group passing
false
:
[1, 2, 3].in_groups_of(2, false) # => [[1, 2], [3]]
As a consequence false
can't be a used as a padding value.
NOTE: Defined in active_support/core_ext/array/grouping.rb
.
in_groups(number, fill_with = nil)
¶ ↑
The method in_groups
splits an array into a certain number of
groups. The method returns an array with the groups:
%w(1 2 3 4 5 6 7).in_groups(3) # => [["1", "2", "3"], ["4", "5", nil], ["6", "7", nil]]
or yields them in turn if a block is passed:
%w(1 2 3 4 5 6 7).in_groups(3) {|group| p group} ["1", "2", "3"] ["4", "5", nil] ["6", "7", nil]
The examples above show that in_groups
fills some groups with
a trailing nil
element as needed. A group can get at most one
of these extra elements, the rightmost one if any. And the groups that have
them are always the last ones.
You can change this padding value using the second optional argument:
%w(1 2 3 4 5 6 7).in_groups(3, "0") # => [["1", "2", "3"], ["4", "5", "0"], ["6", "7", "0"]]
And you can tell the method not to fill the smaller groups passing
false
:
%w(1 2 3 4 5 6 7).in_groups(3, false) # => [["1", "2", "3"], ["4", "5"], ["6", "7"]]
As a consequence false
can't be a used as a padding value.
NOTE: Defined in active_support/core_ext/array/grouping.rb
.
split(value = nil)
¶ ↑
The method split
divides an array by a separator and returns
the resulting chunks.
If a block is passed the separators are those elements of the array for which the block returns true:
(-5..5).to_a.split { |i| i.multiple_of?(4) } # => [[-5], [-3, -2, -1], [1, 2, 3], [5]]
Otherwise, the value received as argument, which defaults to
nil
, is the separator:
[0, 1, -5, 1, 1, "foo", "bar"].split(1) # => [[0], [-5], [], ["foo", "bar"]]
TIP: Observe in the previous example that consecutive separators result in empty arrays.
NOTE: Defined in active_support/core_ext/array/grouping.rb
.
Extensions to Hash
¶ ↑
Conversions¶ ↑
to_xml
¶ ↑
The method to_xml
returns a string containing an XML
representation of its receiver:
{"foo" => 1, "bar" => 2}.to_xml # => # <?xml version="1.0" encoding="UTF-8"?> # <hash> # <foo type="integer">1</foo> # <bar type="integer">2</bar> # </hash>
To do so, the method loops over the pairs and builds nodes that depend on
the values. Given a pair key
, value
:
-
If
value
is a hash there's a recursive call withkey
as:root
. -
If
value
is an array there's a recursive call withkey
as:root
, andkey
singularized as:children
. -
If
value
is a callable object it must expect one or two arguments. Depending on the arity, the callable is invoked with theoptions
hash as first argument withkey
as:root
, andkey
singularized as second argument. Its return value becomes a new node. -
If
value
responds toto_xml
the method is invoked withkey
as:root
. -
Otherwise, a node with
key
as tag is created with a string representation ofvalue
as text node. Ifvalue
isnil
an attribute “nil” set to “true” is added. Unless the option:skip_types
exists and is true, an attribute “type” is added as well according to the following mapping:
XML_TYPE_NAMES = { "Symbol" => "symbol", "Fixnum" => "integer", "Bignum" => "integer", "BigDecimal" => "decimal", "Float" => "float", "TrueClass" => "boolean", "FalseClass" => "boolean", "Date" => "date", "DateTime" => "datetime", "Time" => "datetime" }
By default the root node is “hash”, but that's configurable via the
:root
option.
The default XML builder is a fresh instance of
Builder::XmlMarkup
. You can configure your own builder with
the :builder
option. The method also accepts options like
:dasherize
and friends, they are forwarded to the builder.
NOTE: Defined in active_support/core_ext/hash/conversions.rb
.
Merging¶ ↑
Ruby has a built-in method Hash#merge
that merges two hashes:
{a: 1, b: 1}.merge(a: 0, c: 2) # => {:a=>0, :b=>1, :c=>2}
Active Support defines a few more ways of merging hashes that may be convenient.
reverse_merge
and reverse_merge!
¶ ↑
In case of collision the key in the hash of the argument wins in
merge
. You can support option hashes with default values in a
compact way with this idiom:
options = {length: 30, omission: "..."}.merge(options)
Active Support defines reverse_merge
in case you prefer this
alternative notation:
options = options.reverse_merge(length: 30, omission: "...")
And a bang version reverse_merge!
that performs the merge in
place:
options.reverse_merge!(length: 30, omission: "...")
WARNING. Take into account that reverse_merge!
may change the
hash in the caller, which may or may not be a good idea.
NOTE: Defined in
active_support/core_ext/hash/reverse_merge.rb
.
reverse_update
¶ ↑
The method reverse_update
is an alias for
reverse_merge!
, explained above.
WARNING. Note that reverse_update
has no bang.
NOTE: Defined in
active_support/core_ext/hash/reverse_merge.rb
.
deep_merge
and deep_merge!
¶ ↑
As you can see in the previous example if a key is found in both hashes the value in the one in the argument wins.
Active Support defines Hash#deep_merge
. In a deep merge, if a
key is found in both hashes and their values are hashes in turn, then their
merge becomes the value in the resulting hash:
{a: {b: 1}}.deep_merge(a: {c: 2}) # => {:a=>{:b=>1, :c=>2}}
The method deep_merge!
performs a deep merge in place.
NOTE: Defined in active_support/core_ext/hash/deep_merge.rb
.
Deep duplicating¶ ↑
The method Hash.deep_dup
duplicates itself and all keys and
values inside recursively with Active Support method
Object#deep_dup
. It works like
Enumerator#each_with_object
with sending deep_dup
method to each pair inside.
hash = { a: 1, b: { c: 2, d: [3, 4] } } dup = hash.deep_dup dup[:b][:e] = 5 dup[:b][:d] << 5 hash[:b][:e] == nil # => true hash[:b][:d] == [3, 4] # => true
NOTE: Defined in active_support/core_ext/object/deep_dup.rb
.
Working with Keys¶ ↑
except
and except!
¶ ↑
The method except
returns a hash with the keys in the argument
list removed, if present:
{a: 1, b: 2}.except(:a) # => {:b=>2}
If the receiver responds to convert_key
, the method is called
on each of the arguments. This allows except
to play nice with
hashes with indifferent access for instance:
{a: 1}.with_indifferent_access.except(:a) # => {} {a: 1}.with_indifferent_access.except("a") # => {}
There's also the bang variant except!
that removes keys in
the very receiver.
NOTE: Defined in active_support/core_ext/hash/except.rb
.
transform_keys
and transform_keys!
¶ ↑
The method transform_keys
accepts a block and returns a hash
that has applied the block operations to each of the keys in the receiver:
{nil => nil, 1 => 1, a: :a}.transform_keys { |key| key.to_s.upcase } # => {"" => nil, "A" => :a, "1" => 1}
In case of key collision, one of the values will be chosen. The chosen value may not always be the same given the same hash:
{"a" => 1, a: 2}.transform_keys { |key| key.to_s.upcase } # The result could either be # => {"A"=>2} # or # => {"A"=>1}
This method may be useful for example to build specialized conversions. For
instance stringify_keys
and symbolize_keys
use
transform_keys
to perform their key conversions:
def stringify_keys transform_keys { |key| key.to_s } end ... def symbolize_keys transform_keys { |key| key.to_sym rescue key } end
There's also the bang variant transform_keys!
that applies
the block operations to keys in the very receiver.
Besides that, one can use deep_transform_keys
and
deep_transform_keys!
to perform the block operation on all the
keys in the given hash and all the hashes nested into it. An example of the
result is:
{nil => nil, 1 => 1, nested: {a: 3, 5 => 5}}.deep_transform_keys { |key| key.to_s.upcase } # => {""=>nil, "1"=>1, "NESTED"=>{"A"=>3, "5"=>5}}
NOTE: Defined in active_support/core_ext/hash/keys.rb
.
stringify_keys
and stringify_keys!
¶ ↑
The method stringify_keys
returns a hash that has a
stringified version of the keys in the receiver. It does so by sending
to_s
to them:
{nil => nil, 1 => 1, a: :a}.stringify_keys # => {"" => nil, "a" => :a, "1" => 1}
In case of key collision, one of the values will be chosen. The chosen value may not always be the same given the same hash:
{"a" => 1, a: 2}.stringify_keys # The result could either be # => {"a"=>2} # or # => {"a"=>1}
This method may be useful for example to easily accept both symbols and
strings as options. For instance
ActionView::Helpers::FormHelper
defines:
def to_check_box_tag(options = {}, checked_value = "1", unchecked_value = "0") options = options.stringify_keys options["type"] = "checkbox" ... end
The second line can safely access the “type” key, and let the user to pass
either :type
or “type”.
There's also the bang variant stringify_keys!
that
stringifies keys in the very receiver.
Besides that, one can use deep_stringify_keys
and
deep_stringify_keys!
to stringify all the keys in the given
hash and all the hashes nested into it. An example of the result is:
{nil => nil, 1 => 1, nested: {a: 3, 5 => 5}}.deep_stringify_keys # => {""=>nil, "1"=>1, "nested"=>{"a"=>3, "5"=>5}}
NOTE: Defined in active_support/core_ext/hash/keys.rb
.
symbolize_keys
and symbolize_keys!
¶ ↑
The method symbolize_keys
returns a hash that has a symbolized
version of the keys in the receiver, where possible. It does so by sending
to_sym
to them:
{nil => nil, 1 => 1, "a" => "a"}.symbolize_keys # => {1=>1, nil=>nil, :a=>"a"}
WARNING. Note in the previous example only one key was symbolized.
In case of key collision, one of the values will be chosen. The chosen value may not always be the same given the same hash:
{"a" => 1, a: 2}.symbolize_keys # The result could either be # => {:a=>2} # or # => {:a=>1}
This method may be useful for example to easily accept both symbols and
strings as options. For instance ActionController::UrlRewriter
defines
def rewrite_path(options) options = options.symbolize_keys options.update(options[:params].symbolize_keys) if options[:params] ... end
The second line can safely access the :params
key, and let the
user to pass either :params
or “params”.
There's also the bang variant symbolize_keys!
that
symbolizes keys in the very receiver.
Besides that, one can use deep_symbolize_keys
and
deep_symbolize_keys!
to symbolize all the keys in the given
hash and all the hashes nested into it. An example of the result is:
{nil => nil, 1 => 1, "nested" => {"a" => 3, 5 => 5}}.deep_symbolize_keys # => {nil=>nil, 1=>1, nested:{a:3, 5=>5}}
NOTE: Defined in active_support/core_ext/hash/keys.rb
.
to_options
and to_options!
¶ ↑
The methods to_options
and to_options!
are
respectively aliases of symbolize_keys
and
symbolize_keys!
.
NOTE: Defined in active_support/core_ext/hash/keys.rb
.
assert_valid_keys
¶ ↑
The method assert_valid_keys
receives an arbitrary number of
arguments, and checks whether the receiver has any key outside that white
list. If it does ArgumentError
is raised.
{a: 1}.assert_valid_keys(:a) # passes {a: 1}.assert_valid_keys("a") # ArgumentError
Active Record does not accept unknown options when building associations,
for example. It implements that control via assert_valid_keys
.
NOTE: Defined in active_support/core_ext/hash/keys.rb
.
Working with Values¶ ↑
transform_values
&& transform_values!
¶ ↑
The method transform_values
accepts a block and returns a hash
that has applied the block operations to each of the values in the
receiver.
{ nil => nil, 1 => 1, :x => :a }.transform_values { |value| value.to_s.upcase } # => {nil=>"", 1=>"1", :x=>"A"}
There's also the bang variant transform_values!
that
applies the block operations to values in the very receiver.
NOTE: Defined in
active_support/core_text/hash/transform_values.rb
.
Slicing¶ ↑
Ruby has built-in support for taking slices out of strings and arrays. Active Support extends slicing to hashes:
{a: 1, b: 2, c: 3}.slice(:a, :c) # => {:c=>3, :a=>1} {a: 1, b: 2, c: 3}.slice(:b, :X) # => {:b=>2} # non-existing keys are ignored
If the receiver responds to convert_key
keys are normalized:
{a: 1, b: 2}.with_indifferent_access.slice("a") # => {:a=>1}
NOTE. Slicing may come in handy for sanitizing option hashes with a white list of keys.
There's also slice!
which in addition to perform a slice
in place returns what's removed:
hash = {a: 1, b: 2} rest = hash.slice!(:a) # => {:b=>2} hash # => {:a=>1}
NOTE: Defined in active_support/core_ext/hash/slice.rb
.
Extracting¶ ↑
The method extract!
removes and returns the key/value pairs
matching the given keys.
hash = {a: 1, b: 2} rest = hash.extract!(:a) # => {:a=>1} hash # => {:b=>2}
The method extract!
returns the same subclass of Hash, that
the receiver is.
hash = {a: 1, b: 2}.with_indifferent_access rest = hash.extract!(:a).class # => ActiveSupport::HashWithIndifferentAccess
NOTE: Defined in active_support/core_ext/hash/slice.rb
.
Indifferent Access¶ ↑
The method with_indifferent_access
returns an
ActiveSupport::HashWithIndifferentAccess
out of its receiver:
{a: 1}.with_indifferent_access["a"] # => 1
NOTE: Defined in
active_support/core_ext/hash/indifferent_access.rb
.
Compacting¶ ↑
The methods compact
and compact!
return a Hash
without items with nil
value.
{a: 1, b: 2, c: nil}.compact # => {a: 1, b: 2}
NOTE: Defined in active_support/core_ext/hash/compact.rb
.
Extensions to Regexp
¶ ↑
multiline?
¶ ↑
The method multiline?
says whether a regexp has the
/m
flag set, that is, whether the dot matches newlines.
%r{.}.multiline? # => false %r{.}m.multiline? # => true Regexp.new('.').multiline? # => false Regexp.new('.', Regexp::MULTILINE).multiline? # => true
Rails uses this method in a single place, also in the routing code. Multiline regexps are disallowed for route requirements and this flag eases enforcing that constraint.
def assign_route_options(segments, defaults, requirements) ... if requirement.multiline? raise ArgumentError, "Regexp multiline option not allowed in routing requirements: #{requirement.inspect}" end ... end
NOTE: Defined in active_support/core_ext/regexp.rb
.
Extensions to Range
¶ ↑
to_s
¶ ↑
Active Support extends the method Range#to_s
so that it
understands an optional format argument. As of this writing the only
supported non-default format is :db
:
(Date.today..Date.tomorrow).to_s # => "2009-10-25..2009-10-26" (Date.today..Date.tomorrow).to_s(:db) # => "BETWEEN '2009-10-25' AND '2009-10-26'"
As the example depicts, the :db
format generates a
BETWEEN
SQL clause. That is used by Active Record in its
support for range values in conditions.
NOTE: Defined in active_support/core_ext/range/conversions.rb
.
include?
¶ ↑
The methods Range#include?
and Range#===
say
whether some value falls between the ends of a given instance:
(2..3).include?(Math::E) # => true
Active Support extends these methods so that the argument may be another range in turn. In that case we test whether the ends of the argument range belong to the receiver themselves:
(1..10).include?(3..7) # => true (1..10).include?(0..7) # => false (1..10).include?(3..11) # => false (1...9).include?(3..9) # => false (1..10) === (3..7) # => true (1..10) === (0..7) # => false (1..10) === (3..11) # => false (1...9) === (3..9) # => false
NOTE: Defined in
active_support/core_ext/range/include_range.rb
.
overlaps?
¶ ↑
The method Range#overlaps?
says whether any two given ranges
have non-void intersection:
(1..10).overlaps?(7..11) # => true (1..10).overlaps?(0..7) # => true (1..10).overlaps?(11..27) # => false
NOTE: Defined in active_support/core_ext/range/overlaps.rb
.
Extensions to Date
¶ ↑
Calculations¶ ↑
NOTE: All the following methods are defined in
active_support/core_ext/date/calculations.rb
.
INFO: The following calculation methods have edge cases in October 1582,
since days 5..14 just do not exist. This guide does not document their
behavior around those days for brevity, but it is enough to say that they
do what you would expect. That is, Date.new(1582, 10,
4).tomorrow
returns Date.new(1582, 10, 15)
and so on.
Please check test/core_ext/date_ext_test.rb
in the Active
Support test suite for expected behavior.
Date.current
¶ ↑
Active Support defines Date.current
to be today in the current
time zone. That's like Date.today
, except that it honors
the user time zone, if defined. It also defines Date.yesterday
and Date.tomorrow
, and the instance predicates
past?
, today?
, and future?
, all of
them relative to Date.current
.
When making Date comparisons using methods which honor the user time zone,
make sure to use Date.current
and not Date.today
.
There are cases where the user time zone might be in the future compared to
the system time zone, which Date.today
uses by default. This
means Date.today
may equal Date.yesterday
.
Named dates¶ ↑
prev_year
, next_year
¶ ↑
In Ruby 1.9 prev_year
and next_year
return a date
with the same day/month in the last or next year:
d = Date.new(2010, 5, 8) # => Sat, 08 May 2010 d.prev_year # => Fri, 08 May 2009 d.next_year # => Sun, 08 May 2011
If date is the 29th of February of a leap year, you obtain the 28th:
d = Date.new(2000, 2, 29) # => Tue, 29 Feb 2000 d.prev_year # => Sun, 28 Feb 1999 d.next_year # => Wed, 28 Feb 2001
prev_year
is aliased to last_year
.
prev_month
, next_month
¶ ↑
In Ruby 1.9 prev_month
and next_month
return the
date with the same day in the last or next month:
d = Date.new(2010, 5, 8) # => Sat, 08 May 2010 d.prev_month # => Thu, 08 Apr 2010 d.next_month # => Tue, 08 Jun 2010
If such a day does not exist, the last day of the corresponding month is returned:
Date.new(2000, 5, 31).prev_month # => Sun, 30 Apr 2000 Date.new(2000, 3, 31).prev_month # => Tue, 29 Feb 2000 Date.new(2000, 5, 31).next_month # => Fri, 30 Jun 2000 Date.new(2000, 1, 31).next_month # => Tue, 29 Feb 2000
prev_month
is aliased to last_month
.
prev_quarter
, next_quarter
¶ ↑
Same as prev_month
and next_month
. It returns the
date with the same day in the previous or next quarter:
t = Time.local(2010, 5, 8) # => Sat, 08 May 2010 t.prev_quarter # => Mon, 08 Feb 2010 t.next_quarter # => Sun, 08 Aug 2010
If such a day does not exist, the last day of the corresponding month is returned:
Time.local(2000, 7, 31).prev_quarter # => Sun, 30 Apr 2000 Time.local(2000, 5, 31).prev_quarter # => Tue, 29 Feb 2000 Time.local(2000, 10, 31).prev_quarter # => Mon, 30 Oct 2000 Time.local(2000, 11, 31).next_quarter # => Wed, 28 Feb 2001
prev_quarter
is aliased to last_quarter
.
beginning_of_week
, end_of_week
¶ ↑
The methods beginning_of_week
and end_of_week
return the dates for the beginning and end of the week, respectively. Weeks
are assumed to start on Monday, but that can be changed passing an
argument, setting thread local Date.beginning_of_week
or
config.beginning_of_week
.
d = Date.new(2010, 5, 8) # => Sat, 08 May 2010 d.beginning_of_week # => Mon, 03 May 2010 d.beginning_of_week(:sunday) # => Sun, 02 May 2010 d.end_of_week # => Sun, 09 May 2010 d.end_of_week(:sunday) # => Sat, 08 May 2010
beginning_of_week
is aliased to
at_beginning_of_week
and end_of_week
is aliased
to at_end_of_week
.
monday
, sunday
¶ ↑
The methods monday
and sunday
return the dates
for the previous Monday and next Sunday, respectively.
d = Date.new(2010, 5, 8) # => Sat, 08 May 2010 d.monday # => Mon, 03 May 2010 d.sunday # => Sun, 09 May 2010 d = Date.new(2012, 9, 10) # => Mon, 10 Sep 2012 d.monday # => Mon, 10 Sep 2012 d = Date.new(2012, 9, 16) # => Sun, 16 Sep 2012 d.sunday # => Sun, 16 Sep 2012
prev_week
, next_week
¶ ↑
The method next_week
receives a symbol with a day name in
English (default is the thread local Date.beginning_of_week
,
or config.beginning_of_week
, or :monday
) and it
returns the date corresponding to that day.
d = Date.new(2010, 5, 9) # => Sun, 09 May 2010 d.next_week # => Mon, 10 May 2010 d.next_week(:saturday) # => Sat, 15 May 2010
The method prev_week
is analogous:
d.prev_week # => Mon, 26 Apr 2010 d.prev_week(:saturday) # => Sat, 01 May 2010 d.prev_week(:friday) # => Fri, 30 Apr 2010
prev_week
is aliased to last_week
.
Both next_week
and prev_week
work as expected
when Date.beginning_of_week
or
config.beginning_of_week
are set.
beginning_of_month
, end_of_month
¶ ↑
The methods beginning_of_month
and end_of_month
return the dates for the beginning and end of the month:
d = Date.new(2010, 5, 9) # => Sun, 09 May 2010 d.beginning_of_month # => Sat, 01 May 2010 d.end_of_month # => Mon, 31 May 2010
beginning_of_month
is aliased to
at_beginning_of_month
, and end_of_month
is
aliased to at_end_of_month
.
beginning_of_quarter
, end_of_quarter
¶ ↑
The methods beginning_of_quarter
and
end_of_quarter
return the dates for the beginning and end of
the quarter of the receiver's calendar year:
d = Date.new(2010, 5, 9) # => Sun, 09 May 2010 d.beginning_of_quarter # => Thu, 01 Apr 2010 d.end_of_quarter # => Wed, 30 Jun 2010
beginning_of_quarter
is aliased to
at_beginning_of_quarter
, and end_of_quarter
is
aliased to at_end_of_quarter
.
beginning_of_year
, end_of_year
¶ ↑
The methods beginning_of_year
and end_of_year
return the dates for the beginning and end of the year:
d = Date.new(2010, 5, 9) # => Sun, 09 May 2010 d.beginning_of_year # => Fri, 01 Jan 2010 d.end_of_year # => Fri, 31 Dec 2010
beginning_of_year
is aliased to
at_beginning_of_year
, and end_of_year
is aliased
to at_end_of_year
.
Other Date Computations¶ ↑
years_ago
, years_since
¶ ↑
The method years_ago
receives a number of years and returns
the same date those many years ago:
date = Date.new(2010, 6, 7) date.years_ago(10) # => Wed, 07 Jun 2000
years_since
moves forward in time:
date = Date.new(2010, 6, 7) date.years_since(10) # => Sun, 07 Jun 2020
If such a day does not exist, the last day of the corresponding month is returned:
Date.new(2012, 2, 29).years_ago(3) # => Sat, 28 Feb 2009 Date.new(2012, 2, 29).years_since(3) # => Sat, 28 Feb 2015
months_ago
, months_since
¶ ↑
The methods months_ago
and months_since
work
analogously for months:
Date.new(2010, 4, 30).months_ago(2) # => Sun, 28 Feb 2010 Date.new(2010, 4, 30).months_since(2) # => Wed, 30 Jun 2010
If such a day does not exist, the last day of the corresponding month is returned:
Date.new(2010, 4, 30).months_ago(2) # => Sun, 28 Feb 2010 Date.new(2009, 12, 31).months_since(2) # => Sun, 28 Feb 2010
weeks_ago
¶ ↑
The method weeks_ago
works analogously for weeks:
Date.new(2010, 5, 24).weeks_ago(1) # => Mon, 17 May 2010 Date.new(2010, 5, 24).weeks_ago(2) # => Mon, 10 May 2010
advance
¶ ↑
The most generic way to jump to other days is advance
. This
method receives a hash with keys :years
, :months
,
:weeks
, :days
, and returns a date advanced as
much as the present keys indicate:
date = Date.new(2010, 6, 6) date.advance(years: 1, weeks: 2) # => Mon, 20 Jun 2011 date.advance(months: 2, days: -2) # => Wed, 04 Aug 2010
Note in the previous example that increments may be negative.
To perform the computation the method first increments years, then months, then weeks, and finally days. This order is important towards the end of months. Say for example we are at the end of February of 2010, and we want to move one month and one day forward.
The method advance
advances first one month, and then one day,
the result is:
Date.new(2010, 2, 28).advance(months: 1, days: 1) # => Sun, 29 Mar 2010
While if it did it the other way around the result would be different:
Date.new(2010, 2, 28).advance(days: 1).advance(months: 1) # => Thu, 01 Apr 2010
Changing Components¶ ↑
The method change
allows you to get a new date which is the
same as the receiver except for the given year, month, or day:
Date.new(2010, 12, 23).change(year: 2011, month: 11) # => Wed, 23 Nov 2011
This method is not tolerant to non-existing dates, if the change is invalid
ArgumentError
is raised:
Date.new(2010, 1, 31).change(month: 2) # => ArgumentError: invalid date
Durations¶ ↑
Durations can be added to and subtracted from dates:
d = Date.current # => Mon, 09 Aug 2010 d + 1.year # => Tue, 09 Aug 2011 d - 3.hours # => Sun, 08 Aug 2010 21:00:00 UTC +00:00
They translate to calls to since
or advance
. For
example here we get the correct jump in the calendar reform:
Date.new(1582, 10, 4) + 1.day # => Fri, 15 Oct 1582
Timestamps¶ ↑
INFO: The following methods return a Time
object if possible,
otherwise a DateTime
. If set, they honor the user time zone.
beginning_of_day
, end_of_day
¶ ↑
The method beginning_of_day
returns a timestamp at the
beginning of the day (00:00:00):
date = Date.new(2010, 6, 7) date.beginning_of_day # => Mon Jun 07 00:00:00 +0200 2010
The method end_of_day
returns a timestamp at the end of the
day (23:59:59):
date = Date.new(2010, 6, 7) date.end_of_day # => Mon Jun 07 23:59:59 +0200 2010
beginning_of_day
is aliased to
at_beginning_of_day
, midnight
,
at_midnight
.
beginning_of_hour
, end_of_hour
¶ ↑
The method beginning_of_hour
returns a timestamp at the
beginning of the hour (hh:00:00):
date = DateTime.new(2010, 6, 7, 19, 55, 25) date.beginning_of_hour # => Mon Jun 07 19:00:00 +0200 2010
The method end_of_hour
returns a timestamp at the end of the
hour (hh:59:59):
date = DateTime.new(2010, 6, 7, 19, 55, 25) date.end_of_hour # => Mon Jun 07 19:59:59 +0200 2010
beginning_of_hour
is aliased to
at_beginning_of_hour
.
beginning_of_minute
, end_of_minute
¶ ↑
The method beginning_of_minute
returns a timestamp at the
beginning of the minute (hh:mm:00):
date = DateTime.new(2010, 6, 7, 19, 55, 25) date.beginning_of_minute # => Mon Jun 07 19:55:00 +0200 2010
The method end_of_minute
returns a timestamp at the end of the
minute (hh:mm:59):
date = DateTime.new(2010, 6, 7, 19, 55, 25) date.end_of_minute # => Mon Jun 07 19:55:59 +0200 2010
beginning_of_minute
is aliased to
at_beginning_of_minute
.
INFO: beginning_of_hour
, end_of_hour
,
beginning_of_minute
and end_of_minute
are
implemented for Time
and DateTime
but
not Date
as it does not make sense to request
the beginning or end of an hour or minute on a Date
instance.
ago
, since
¶ ↑
The method ago
receives a number of seconds as argument and
returns a timestamp those many seconds ago from midnight:
date = Date.current # => Fri, 11 Jun 2010 date.ago(1) # => Thu, 10 Jun 2010 23:59:59 EDT -04:00
Similarly, since
moves forward:
date = Date.current # => Fri, 11 Jun 2010 date.since(1) # => Fri, 11 Jun 2010 00:00:01 EDT -04:00
Other Time Computations¶ ↑
Conversions¶ ↑
Extensions to DateTime
¶ ↑
WARNING: DateTime
is not aware of DST rules and so some of
these methods have edge cases when a DST change is going on. For example
seconds_since_midnight
might not return the real amount in
such a day.
Calculations¶ ↑
NOTE: All the following methods are defined in
active_support/core_ext/date_time/calculations.rb
.
The class DateTime
is a subclass of Date
so by
loading active_support/core_ext/date/calculations.rb
you
inherit these methods and their aliases, except that they will always
return datetimes:
yesterday tomorrow beginning_of_week (at_beginning_of_week) end_of_week (at_end_of_week) monday sunday weeks_ago prev_week (last_week) next_week months_ago months_since beginning_of_month (at_beginning_of_month) end_of_month (at_end_of_month) prev_month (last_month) next_month beginning_of_quarter (at_beginning_of_quarter) end_of_quarter (at_end_of_quarter) beginning_of_year (at_beginning_of_year) end_of_year (at_end_of_year) years_ago years_since prev_year (last_year) next_year
The following methods are reimplemented so you do not need
to load active_support/core_ext/date/calculations.rb
for these
ones:
beginning_of_day (midnight, at_midnight, at_beginning_of_day) end_of_day ago since (in)
On the other hand, advance
and change
are also
defined and support more options, they are documented below.
The following methods are only implemented in
active_support/core_ext/date_time/calculations.rb
as they only
make sense when used with a DateTime
instance:
beginning_of_hour (at_beginning_of_hour) end_of_hour
Named Datetimes¶ ↑
DateTime.current
¶ ↑
Active Support defines DateTime.current
to be like
Time.now.to_datetime
, except that it honors the user time
zone, if defined. It also defines DateTime.yesterday
and
DateTime.tomorrow
, and the instance predicates
past?
, and future?
relative to
DateTime.current
.
Other Extensions¶ ↑
seconds_since_midnight
¶ ↑
The method seconds_since_midnight
returns the number of
seconds since midnight:
now = DateTime.current # => Mon, 07 Jun 2010 20:26:36 +0000 now.seconds_since_midnight # => 73596
utc
¶ ↑
The method utc
gives you the same datetime in the receiver
expressed in UTC.
now = DateTime.current # => Mon, 07 Jun 2010 19:27:52 -0400 now.utc # => Mon, 07 Jun 2010 23:27:52 +0000
This method is also aliased as getutc
.
utc?
¶ ↑
The predicate utc?
says whether the receiver has UTC as its
time zone:
now = DateTime.now # => Mon, 07 Jun 2010 19:30:47 -0400 now.utc? # => false now.utc.utc? # => true
advance
¶ ↑
The most generic way to jump to another datetime is advance
.
This method receives a hash with keys :years
,
:months
, :weeks
, :days
,
:hours
, :minutes
, and :seconds
, and
returns a datetime advanced as much as the present keys indicate.
d = DateTime.current # => Thu, 05 Aug 2010 11:33:31 +0000 d.advance(years: 1, months: 1, days: 1, hours: 1, minutes: 1, seconds: 1) # => Tue, 06 Sep 2011 12:34:32 +0000
This method first computes the destination date passing
:years
, :months
, :weeks
, and
:days
to Date#advance
documented above. After
that, it adjusts the time calling since
with the number of
seconds to advance. This order is relevant, a different ordering would give
different datetimes in some edge-cases. The example in
Date#advance
applies, and we can extend it to show order
relevance related to the time bits.
If we first move the date bits (that have also a relative order of processing, as documented before), and then the time bits we get for example the following computation:
d = DateTime.new(2010, 2, 28, 23, 59, 59) # => Sun, 28 Feb 2010 23:59:59 +0000 d.advance(months: 1, seconds: 1) # => Mon, 29 Mar 2010 00:00:00 +0000
but if we computed them the other way around, the result would be different:
d.advance(seconds: 1).advance(months: 1) # => Thu, 01 Apr 2010 00:00:00 +0000
WARNING: Since DateTime
is not DST-aware you can end up in a
non-existing point in time with no warning or error telling you so.
Changing Components¶ ↑
The method change
allows you to get a new datetime which is
the same as the receiver except for the given options, which may include
:year
, :month
, :day
,
:hour
, :min
, :sec
,
:offset
, :start
:
now = DateTime.current # => Tue, 08 Jun 2010 01:56:22 +0000 now.change(year: 2011, offset: Rational(-6, 24)) # => Wed, 08 Jun 2011 01:56:22 -0600
If hours are zeroed, then minutes and seconds are too (unless they have given values):
now.change(hour: 0) # => Tue, 08 Jun 2010 00:00:00 +0000
Similarly, if minutes are zeroed, then seconds are too (unless it has given a value):
now.change(min: 0) # => Tue, 08 Jun 2010 01:00:00 +0000
This method is not tolerant to non-existing dates, if the change is invalid
ArgumentError
is raised:
DateTime.current.change(month: 2, day: 30) # => ArgumentError: invalid date
Durations¶ ↑
Durations can be added to and subtracted from datetimes:
now = DateTime.current # => Mon, 09 Aug 2010 23:15:17 +0000 now + 1.year # => Tue, 09 Aug 2011 23:15:17 +0000 now - 1.week # => Mon, 02 Aug 2010 23:15:17 +0000
They translate to calls to since
or advance
. For
example here we get the correct jump in the calendar reform:
DateTime.new(1582, 10, 4, 23) + 1.hour # => Fri, 15 Oct 1582 00:00:00 +0000
Extensions to Time
¶ ↑
Calculations¶ ↑
NOTE: All the following methods are defined in
active_support/core_ext/time/calculations.rb
.
Active Support adds to Time
many of the methods available for
DateTime
:
past? today? future? yesterday tomorrow seconds_since_midnight change advance ago since (in) beginning_of_day (midnight, at_midnight, at_beginning_of_day) end_of_day beginning_of_hour (at_beginning_of_hour) end_of_hour beginning_of_week (at_beginning_of_week) end_of_week (at_end_of_week) monday sunday weeks_ago prev_week (last_week) next_week months_ago months_since beginning_of_month (at_beginning_of_month) end_of_month (at_end_of_month) prev_month (last_month) next_month beginning_of_quarter (at_beginning_of_quarter) end_of_quarter (at_end_of_quarter) beginning_of_year (at_beginning_of_year) end_of_year (at_end_of_year) years_ago years_since prev_year (last_year) next_year
They are analogous. Please refer to their documentation above and take into account the following differences:
-
change
accepts an additional:usec
option. -
Time
understands DST, so you get correct DST calculations as in
Time.zone_default # => #<ActiveSupport::TimeZone:0x7f73654d4f38 @utc_offset=nil, @name="Madrid", ...> # In Barcelona, 2010/03/28 02:00 +0100 becomes 2010/03/28 03:00 +0200 due to DST. t = Time.local(2010, 3, 28, 1, 59, 59) # => Sun Mar 28 01:59:59 +0100 2010 t.advance(seconds: 1) # => Sun Mar 28 03:00:00 +0200 2010
-
If
since
orago
jump to a time that can't be expressed withTime
aDateTime
object is returned instead.
Time.current
¶ ↑
Active Support defines Time.current
to be today in the current
time zone. That's like Time.now
, except that it honors the
user time zone, if defined. It also defines the instance predicates
past?
, today?
, and future?
, all of
them relative to Time.current
.
When making Time comparisons using methods which honor the user time zone,
make sure to use Time.current
instead of
Time.now
. There are cases where the user time zone might be in
the future compared to the system time zone, which Time.now
uses by default. This means Time.now.to_date
may equal
Date.yesterday
.
all_day
, all_week
, all_month
, all_quarter
and all_year
¶ ↑
The method all_day
returns a range representing the whole day
of the current time.
now = Time.current # => Mon, 09 Aug 2010 23:20:05 UTC +00:00 now.all_day # => Mon, 09 Aug 2010 00:00:00 UTC +00:00..Mon, 09 Aug 2010 23:59:59 UTC +00:00
Analogously, all_week
, all_month
,
all_quarter
and all_year
all serve the purpose of
generating time ranges.
now = Time.current # => Mon, 09 Aug 2010 23:20:05 UTC +00:00 now.all_week # => Mon, 09 Aug 2010 00:00:00 UTC +00:00..Sun, 15 Aug 2010 23:59:59 UTC +00:00 now.all_week(:sunday) # => Sun, 16 Sep 2012 00:00:00 UTC +00:00..Sat, 22 Sep 2012 23:59:59 UTC +00:00 now.all_month # => Sat, 01 Aug 2010 00:00:00 UTC +00:00..Tue, 31 Aug 2010 23:59:59 UTC +00:00 now.all_quarter # => Thu, 01 Jul 2010 00:00:00 UTC +00:00..Thu, 30 Sep 2010 23:59:59 UTC +00:00 now.all_year # => Fri, 01 Jan 2010 00:00:00 UTC +00:00..Fri, 31 Dec 2010 23:59:59 UTC +00:00
Time Constructors¶ ↑
Active Support defines Time.current
to be
Time.zone.now
if there's a user time zone defined, with
fallback to Time.now
:
Time.zone_default # => #<ActiveSupport::TimeZone:0x7f73654d4f38 @utc_offset=nil, @name="Madrid", ...> Time.current # => Fri, 06 Aug 2010 17:11:58 CEST +02:00
Analogously to DateTime
, the predicates past?
,
and future?
are relative to Time.current
.
If the time to be constructed lies beyond the range supported by
Time
in the runtime platform, usecs are discarded and a
DateTime
object is returned instead.
Durations¶ ↑
Durations can be added to and subtracted from time objects:
now = Time.current # => Mon, 09 Aug 2010 23:20:05 UTC +00:00 now + 1.year # => Tue, 09 Aug 2011 23:21:11 UTC +00:00 now - 1.week # => Mon, 02 Aug 2010 23:21:11 UTC +00:00
They translate to calls to since
or advance
. For
example here we get the correct jump in the calendar reform:
Time.utc(1582, 10, 3) + 5.days # => Mon Oct 18 00:00:00 UTC 1582
Extensions to File
¶ ↑
atomic_write
¶ ↑
With the class method File.atomic_write
you can write to a
file in a way that will prevent any reader from seeing half-written
content.
The name of the file is passed as an argument, and the method yields a file
handle opened for writing. Once the block is done atomic_write
closes the file handle and completes its job.
For example, Action Pack uses this method to write asset cache files like
all.css
:
File.atomic_write(joined_asset_path) do |cache| cache.write(join_asset_file_contents(asset_paths)) end
To accomplish this atomic_write
creates a temporary file.
That's the file the code in the block actually writes to. On
completion, the temporary file is renamed, which is an atomic operation on
POSIX systems. If the target file exists atomic_write
overwrites it and keeps owners and permissions. However there are a few
cases where atomic_write
cannot change the file ownership or
permissions, this error is caught and skipped over trusting in the
user/filesystem to ensure the file is accessible to the processes that need
it.
NOTE. Due to the chmod operation atomic_write
performs, if the
target file has an ACL set on it this ACL will be recalculated/modified.
WARNING. Note you can't append with atomic_write
.
The auxiliary file is written in a standard directory for temporary files, but you can pass a directory of your choice as second argument.
NOTE: Defined in active_support/core_ext/file/atomic.rb
.
Extensions to Marshal
¶ ↑
load
¶ ↑
Active Support adds constant autoloading support to load
.
For example, the file cache store deserializes this way:
File.open(file_name) { |f| Marshal.load(f) }
If the cached data refers to a constant that is unknown at that point, the autoloading mechanism is triggered and if it succeeds the deserialization is retried transparently.
WARNING. If the argument is an IO
it needs to respond to
rewind
to be able to retry. Regular files respond to
rewind
.
NOTE: Defined in active_support/core_ext/marshal.rb
.
Extensions to Logger
¶ ↑
around_[level]
¶ ↑
Takes two arguments, a before_message
and
after_message
and calls the current level method on the
Logger
instance, passing in the before_message
,
then the specified message, then the after_message
:
logger = Logger.new("log/development.log") logger.around_info("before", "after") { |logger| logger.info("during") }
silence
¶ ↑
Silences every log level lesser to the specified one for the duration of the given block. Log level orders are: debug, info, error and fatal.
logger = Logger.new("log/development.log") logger.silence(Logger::INFO) do logger.debug("In space, no one can hear you scream.") logger.info("Scream all you want, small mailman!") end
datetime_format=
¶ ↑
Modifies the datetime format output by the formatter class associated with
this logger. If the formatter class does not have a
datetime_format
method then this is ignored.
class Logger::FormatWithTime < Logger::Formatter cattr_accessor(:datetime_format) { "%Y%m%d%H%m%S" } def self.call(severity, timestamp, progname, msg) "#{timestamp.strftime(datetime_format)} -- #{String === msg ? msg : msg.inspect}\n" end end logger = Logger.new("log/development.log") logger.formatter = Logger::FormatWithTime logger.info("<- is the current time")
NOTE: Defined in active_support/core_ext/logger.rb
.
Extensions to NameError
¶ ↑
Active Support adds missing_name?
to NameError
,
which tests whether the exception was raised because of the name passed as
argument.
The name may be given as a symbol or string. A symbol is tested against the bare constant name, a string is against the fully-qualified constant name.
TIP: A symbol can represent a fully-qualified constant name as in
:"ActiveRecord::Base"
, so the behavior for symbols
is defined for convenience, not because it has to be that way technically.
For example, when an action of ArticlesController
is called
Rails tries optimistically to use ArticlesHelper
. It is OK
that the helper module does not exist, so if an exception for that constant
name is raised it should be silenced. But it could be the case that
articles_helper.rb
raises a NameError
due to an
actual unknown constant. That should be reraised. The method
missing_name?
provides a way to distinguish both cases:
def default_helper_module! module_name = name.sub(/Controller$/, '') module_path = module_name.underscore helper module_path rescue MissingSourceFile => e raise e unless e.is_missing? "helpers/#{module_path}_helper" rescue NameError => e raise e unless e.missing_name? "#{module_name}Helper" end
NOTE: Defined in active_support/core_ext/name_error.rb
.
Extensions to LoadError
¶ ↑
Active Support adds is_missing?
to LoadError
, and
also assigns that class to the constant MissingSourceFile
for
backwards compatibility.
Given a path name is_missing?
tests whether the exception was
raised due to that particular file (except perhaps for the “.rb”
extension).
For example, when an action of ArticlesController
is called
Rails tries to load articles_helper.rb
, but that file may not
exist. That's fine, the helper module is not mandatory so Rails
silences a load error. But it could be the case that the helper module does
exist and in turn requires another library that is missing. In that case
Rails must reraise the exception. The method is_missing?
provides a way to distinguish both cases:
def default_helper_module! module_name = name.sub(/Controller$/, '') module_path = module_name.underscore helper module_path rescue MissingSourceFile => e raise e unless e.is_missing? "helpers/#{module_path}_helper" rescue NameError => e raise e unless e.missing_name? "#{module_name}Helper" end
NOTE: Defined in active_support/core_ext/load_error.rb
.