Extends the module object with class/module and instance accessors for class/module attributes, just like the native attr* accessors for instance attributes.
Extends the module object with class/module and instance accessors for class/module attributes, just like the native attr* accessors for instance attributes, but does so on a per-thread basis.
So the values are scoped within the Thread.current space under the class name of the module.
Extends the API for constants to be able to deal with qualified names. Arguments are assumed to be relative to the receiver.
- MODULE Module::Concerning
- CLASS Module::DelegationError
- A
- C
- D
- M
- P
- Q
- R
- T
RUBY_RESERVED_KEYWORDS | = | %w(alias and BEGIN begin break case class def defined? do else elsif END end ensure false for if in module next nil not or redo rescue retry return self super then true undef unless until when while yield) |
DELEGATION_RESERVED_KEYWORDS | = | %w(_ arg args block) |
DELEGATION_RESERVED_METHOD_NAMES | = | Set.new( RUBY_RESERVED_KEYWORDS + DELEGATION_RESERVED_KEYWORDS ).freeze |
[RW] | attr_internal_naming_format |
Allows you to make aliases for attributes, which includes getter, setter, and a predicate.
class Content < ActiveRecord::Base
# has a title attribute
end
class Email < Content
alias_attribute :subject, :title
end
e = Email.find(1)
e.title # => "Superstars"
e.subject # => "Superstars"
e.subject? # => true
e.subject = "Megastars"
e.title # => "Megastars"
# File activesupport/lib/active_support/core_ext/module/aliasing.rb, line 67 def alias_attribute(new_name, old_name) module_eval " def #{new_name}; self.#{old_name}; end # def subject; self.title; end def #{new_name}?; self.#{old_name}?; end # def subject?; self.title?; end def #{new_name}=(v); self.#{old_name} = v; end # def subject=(v); self.title = v; end ", __FILE__, __LINE__ + 1 end
NOTE: This method is deprecated. Please use Module#prepend
that comes with Ruby 2.0 or newer instead.
Encapsulates the common pattern of:
alias_method :foo_without_feature, :foo
alias_method :foo, :foo_with_feature
With this, you simply do:
alias_method_chain :foo, :feature
And both aliases are set up for you.
Query and bang methods (foo?, foo!) keep the same punctuation:
alias_method_chain :foo?, :feature
is equivalent to
alias_method :foo_without_feature?, :foo?
alias_method :foo?, :foo_with_feature?
so you can safely chain foo, foo?, foo! and/or foo= with the same feature.
# File activesupport/lib/active_support/core_ext/module/aliasing.rb, line 26 def alias_method_chain(target, feature) ActiveSupport::Deprecation.warn("alias_method_chain is deprecated. Please, use Module#prepend instead. From module, you can access the original method using super.") # Strip out punctuation on predicates, bang or writer methods since # e.g. target?_without_feature is not a valid method name. aliased_target, punctuation = target.to_s.sub(/([?!=])$/, ''), $1 yield(aliased_target, punctuation) if block_given? with_method = "#{aliased_target}_with_#{feature}#{punctuation}" without_method = "#{aliased_target}_without_#{feature}#{punctuation}" alias_method without_method, target alias_method target, with_method case when public_method_defined?(without_method) public target when protected_method_defined?(without_method) protected target when private_method_defined?(without_method) private target end end
A module may or may not have a name.
module M; end
M.name # => "M"
m = Module.new
m.name # => nil
anonymous?
method returns true if module does not have a name,
false otherwise:
Module.new.anonymous? # => true
module M; end
M.anonymous? # => false
A module gets a name when it is first assigned to a constant. Either via
the module
or class
keyword or by an explicit
assignment:
m = Module.new # creates an anonymous module
m.anonymous? # => true
M = m # m gets a name here as a side-effect
m.name # => "M"
m.anonymous? # => false
Declares an attribute reader and writer backed by an internally-named instance variable.
Declares an attribute reader backed by an internally-named instance variable.
Declares an attribute writer backed by an internally-named instance variable.
Provides a delegate
class method to easily expose contained
objects' public methods as your own.
Options
-
:to
- Specifies the target object -
:prefix
- Prefixes the new method with the target name or a custom prefix -
:allow_nil
- if set to true, prevents aNoMethodError
from being raised
The macro receives one or more method names (specified as symbols or
strings) and the name of the target object via the :to
option
(also a symbol or string).
Delegation is particularly useful with Active Record associations:
class Greeter < ActiveRecord::Base
def hello
'hello'
end
def goodbye
'goodbye'
end
end
class Foo < ActiveRecord::Base
belongs_to :greeter
delegate :hello, to: :greeter
end
Foo.new.hello # => "hello"
Foo.new.goodbye # => NoMethodError: undefined method `goodbye' for #<Foo:0x1af30c>
Multiple delegates to the same target are allowed:
class Foo < ActiveRecord::Base
belongs_to :greeter
delegate :hello, :goodbye, to: :greeter
end
Foo.new.goodbye # => "goodbye"
Methods can be delegated to instance variables, class variables, or constants by providing them as a symbols:
class Foo
CONSTANT_ARRAY = [0,1,2,3]
@@class_array = [4,5,6,7]
def initialize
@instance_array = [8,9,10,11]
end
delegate :sum, to: :CONSTANT_ARRAY
delegate :min, to: :@@class_array
delegate :max, to: :@instance_array
end
Foo.new.sum # => 6
Foo.new.min # => 4
Foo.new.max # => 11
It's also possible to delegate a method to the class by using
:class
:
class Foo
def self.hello
"world"
end
delegate :hello, to: :class
end
Foo.new.hello # => "world"
Delegates can optionally be prefixed using the :prefix
option.
If the value is true
, the delegate methods are prefixed with
the name of the object being delegated to.
Person = Struct.new(:name, :address)
class Invoice < Struct.new(:client)
delegate :name, :address, to: :client, prefix: true
end
john_doe = Person.new('John Doe', 'Vimmersvej 13')
invoice = Invoice.new(john_doe)
invoice.client_name # => "John Doe"
invoice.client_address # => "Vimmersvej 13"
It is also possible to supply a custom prefix.
class Invoice < Struct.new(:client)
delegate :name, :address, to: :client, prefix: :customer
end
invoice = Invoice.new(john_doe)
invoice.customer_name # => 'John Doe'
invoice.customer_address # => 'Vimmersvej 13'
If the target is nil
and does not respond to the delegated
method a NoMethodError
is raised, as with any other value.
Sometimes, however, it makes sense to be robust to that situation and that
is the purpose of the :allow_nil
option: If the target is not
nil
, or it is and responds to the method, everything works as
usual. But if it is nil
and does not respond to the delegated
method, nil
is returned.
class User < ActiveRecord::Base
has_one :profile
delegate :age, to: :profile
end
User.new.age # raises NoMethodError: undefined method `age'
But if not having a profile yet is fine and should not be an error condition:
class User < ActiveRecord::Base
has_one :profile
delegate :age, to: :profile, allow_nil: true
end
User.new.age # nil
Note that if the target is not nil
then the call is attempted
regardless of the :allow_nil
option, and thus an exception is
still raised if said object does not respond to the method:
class Foo
def initialize(bar)
@bar = bar
end
delegate :name, to: :@bar, allow_nil: true
end
Foo.new("Bar").name # raises NoMethodError: undefined method `name'
The target method must be public, otherwise it will raise
NoMethodError
.
# File activesupport/lib/active_support/core_ext/module/delegation.rb, line 153 def delegate(*methods, to: nil, prefix: nil, allow_nil: nil) unless to raise ArgumentError, 'Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, to: :greeter).' end if prefix == true && to =~ /^[^a-z_]/ raise ArgumentError, 'Can only automatically set the delegation prefix when delegating to a method.' end method_prefix = if prefix "#{prefix == true ? to : prefix}_" else '' end location = caller_locations(1, 1).first file, line = location.path, location.lineno to = to.to_s to = "self.#{to}" if DELEGATION_RESERVED_METHOD_NAMES.include?(to) methods.each do |method| # Attribute writer methods only accept one argument. Makes sure []= # methods still accept two arguments. definition = (method =~ /[^\]]=$/) ? 'arg' : '*args, &block' # The following generated method calls the target exactly once, storing # the returned value in a dummy variable. # # Reason is twofold: On one hand doing less calls is in general better. # On the other hand it could be that the target has side-effects, # whereas conceptually, from the user point of view, the delegator should # be doing one call. if allow_nil method_def = [ "def #{method_prefix}#{method}(#{definition})", "_ = #{to}", "if !_.nil? || nil.respond_to?(:#{method})", " _.#{method}(#{definition})", "end", "end" ].join ';' else exception = %Q(raise DelegationError, "#{self}##{method_prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}") method_def = [ "def #{method_prefix}#{method}(#{definition})", " _ = #{to}", " _.#{method}(#{definition})", "rescue NoMethodError => e", " if _.nil? && e.name == :#{method}", " #{exception}", " else", " raise", " end", "end" ].join ';' end module_eval(method_def, file, line) end end
deprecate :foo
deprecate bar: 'message'
deprecate :foo, :bar, baz: 'warning!', qux: 'gone!'
You can also use custom deprecator instance:
deprecate :foo, deprecator: MyLib::Deprecator.new
deprecate :foo, bar: "warning!", deprecator: MyLib::Deprecator.new
Custom deprecators must respond to
deprecation_warning(deprecated_method_name, message,
caller_backtrace)
method where you can implement your custom warning
behavior.
class MyLib::Deprecator
def deprecation_warning(deprecated_method_name, message, caller_backtrace = nil)
message = "#{deprecated_method_name} is deprecated and will be removed from MyLibrary | #{message}"
Kernel.warn message
end
end
Defines both class and instance accessors for class attributes.
module HairColors
mattr_accessor :hair_colors
end
class Person
include HairColors
end
HairColors.hair_colors = [:brown, :black, :blonde, :red]
HairColors.hair_colors # => [:brown, :black, :blonde, :red]
Person.new.hair_colors # => [:brown, :black, :blonde, :red]
If a subclass changes the value then that would also change the value for parent class. Similarly if parent class changes the value then that would change the value of subclasses too.
class Male < Person
end
Male.new.hair_colors << :blue
Person.new.hair_colors # => [:brown, :black, :blonde, :red, :blue]
To opt out of the instance writer method, pass instance_writer:
false
. To opt out of the instance reader method, pass
instance_reader: false
.
module HairColors
mattr_accessor :hair_colors, instance_writer: false, instance_reader: false
end
class Person
include HairColors
end
Person.new.hair_colors = [:brown] # => NoMethodError
Person.new.hair_colors # => NoMethodError
Or pass instance_accessor: false
, to opt out both instance
methods.
module HairColors
mattr_accessor :hair_colors, instance_accessor: false
end
class Person
include HairColors
end
Person.new.hair_colors = [:brown] # => NoMethodError
Person.new.hair_colors # => NoMethodError
Also you can pass a block to set up the attribute with a default value.
module HairColors
mattr_accessor :hair_colors do
[:brown, :black, :blonde, :red]
end
end
class Person
include HairColors
end
Person.class_variable_get("@@hair_colors") # => [:brown, :black, :blonde, :red]
Defines a class attribute and creates a class and instance reader methods.
The underlying class variable is set to nil
, if it is not
previously defined.
module HairColors
mattr_reader :hair_colors
end
HairColors.hair_colors # => nil
HairColors.class_variable_set("@@hair_colors", [:brown, :black])
HairColors.hair_colors # => [:brown, :black]
The attribute name must be a valid method name in Ruby.
module Foo
mattr_reader :"1_Badname"
end
# => NameError: invalid attribute name: 1_Badname
If you want to opt out the creation on the instance reader method, pass
instance_reader: false
or instance_accessor:
false
.
module HairColors
mattr_reader :hair_colors, instance_reader: false
end
class Person
include HairColors
end
Person.new.hair_colors # => NoMethodError
Also, you can pass a block to set up the attribute with a default value.
module HairColors
mattr_reader :hair_colors do
[:brown, :black, :blonde, :red]
end
end
class Person
include HairColors
end
Person.new.hair_colors # => [:brown, :black, :blonde, :red]
# File activesupport/lib/active_support/core_ext/module/attribute_accessors.rb, line 53 def mattr_reader(*syms) options = syms.extract_options! syms.each do |sym| raise NameError.new("invalid attribute name: #{sym}") unless sym =~ /\A[_A-Za-z]\w*\z/ class_eval(" @@#{sym} = nil unless defined? @@#{sym} def self.#{sym} @@#{sym} end ", __FILE__, __LINE__ + 1) unless options[:instance_reader] == false || options[:instance_accessor] == false class_eval(" def #{sym} @@#{sym} end ", __FILE__, __LINE__ + 1) end class_variable_set("@@#{sym}", yield) if block_given? end end
Defines a class attribute and creates a class and instance writer methods to allow assignment to the attribute.
module HairColors
mattr_writer :hair_colors
end
class Person
include HairColors
end
HairColors.hair_colors = [:brown, :black]
Person.class_variable_get("@@hair_colors") # => [:brown, :black]
Person.new.hair_colors = [:blonde, :red]
HairColors.class_variable_get("@@hair_colors") # => [:blonde, :red]
If you want to opt out the instance writer method, pass
instance_writer: false
or instance_accessor:
false
.
module HairColors
mattr_writer :hair_colors, instance_writer: false
end
class Person
include HairColors
end
Person.new.hair_colors = [:blonde, :red] # => NoMethodError
Also, you can pass a block to set up the attribute with a default value.
module HairColors
mattr_writer :hair_colors do
[:brown, :black, :blonde, :red]
end
end
class Person
include HairColors
end
Person.class_variable_get("@@hair_colors") # => [:brown, :black, :blonde, :red]
# File activesupport/lib/active_support/core_ext/module/attribute_accessors.rb, line 119 def mattr_writer(*syms) options = syms.extract_options! syms.each do |sym| raise NameError.new("invalid attribute name: #{sym}") unless sym =~ /\A[_A-Za-z]\w*\z/ class_eval(" @@#{sym} = nil unless defined? @@#{sym} def self.#{sym}=(obj) @@#{sym} = obj end ", __FILE__, __LINE__ + 1) unless options[:instance_writer] == false || options[:instance_accessor] == false class_eval(" def #{sym}=(obj) @@#{sym} = obj end ", __FILE__, __LINE__ + 1) end send("#{sym}=", yield) if block_given? end end
Returns the module which contains this one according to its name.
module M
module N
end
end
X = M::N
M::N.parent # => M
X.parent # => M
The parent of top-level and anonymous modules is Object.
M.parent # => Object
Module.new.parent # => Object
Returns the name of the module containing this one.
M::N.parent_name # => "M"
Returns all the parents of this module according to its name, ordered from nested outwards. The receiver is not contained within the result.
module M
module N
end
end
X = M::N
M.parents # => [Object]
M::N.parents # => [M, Object]
X.parents # => [M, Object]
# File activesupport/lib/active_support/core_ext/module/introspection.rb, line 48 def parents parents = [] if parent_name parts = parent_name.split('::') until parts.empty? parents << ActiveSupport::Inflector.constantize(parts * '::') parts.pop end end parents << Object unless parents.include? Object parents end
# File activesupport/lib/active_support/core_ext/module/qualified_const.rb, line 29 def qualified_const_defined?(path, search_parents=true) ActiveSupport::Deprecation.warn(" Module#qualified_const_defined? is deprecated in favour of the builtin Module#const_defined? and will be removed in Rails 5.1. ".squish) ActiveSupport::QualifiedConstUtils.raise_if_absolute(path) ActiveSupport::QualifiedConstUtils.names(path).inject(self) do |mod, name| return unless mod.const_defined?(name, search_parents) mod.const_get(name) end return true end
# File activesupport/lib/active_support/core_ext/module/qualified_const.rb, line 44 def qualified_const_get(path) ActiveSupport::Deprecation.warn(" Module#qualified_const_get is deprecated in favour of the builtin Module#const_get and will be removed in Rails 5.1. ".squish) ActiveSupport::QualifiedConstUtils.raise_if_absolute(path) ActiveSupport::QualifiedConstUtils.names(path).inject(self) do |mod, name| mod.const_get(name) end end
# File activesupport/lib/active_support/core_ext/module/qualified_const.rb, line 57 def qualified_const_set(path, value) ActiveSupport::Deprecation.warn(" Module#qualified_const_set is deprecated in favour of the builtin Module#const_set and will be removed in Rails 5.1. ".squish) ActiveSupport::QualifiedConstUtils.raise_if_absolute(path) const_name = path.demodulize mod_name = path.deconstantize mod = mod_name.empty? ? self : const_get(mod_name) mod.const_set(const_name, value) end
Replaces the existing method definition, if there is one, with the passed block as its body.
Removes the named method, if it exists.
Removes the named singleton method, if it exists.
Defines both class and instance accessors for class attributes.
class Account
thread_mattr_accessor :user
end
Account.user = "DHH"
Account.user # => "DHH"
Account.new.user # => "DHH"
If a subclass changes the value, the parent class' value is not changed. Similarly, if the parent class changes the value, the value of subclasses is not changed.
class Customer < Account
end
Customer.user = "Rafael"
Customer.user # => "Rafael"
Account.user # => "DHH"
To opt out of the instance writer method, pass instance_writer:
false
. To opt out of the instance reader method, pass
instance_reader: false
.
class Current
thread_mattr_accessor :user, instance_writer: false, instance_reader: false
end
Current.new.user = "DHH" # => NoMethodError
Current.new.user # => NoMethodError
Or pass instance_accessor: false
, to opt out both instance
methods.
class Current
mattr_accessor :user, instance_accessor: false
end
Current.new.user = "DHH" # => NoMethodError
Current.new.user # => NoMethodError