Class: Module

Inherits:
Object show all
Defined in:
activesupport/lib/active_support/core_ext/object/duplicable.rb,
activesupport/lib/active_support/core_ext/module/aliasing.rb,
activesupport/lib/active_support/core_ext/module/reachable.rb,
activesupport/lib/active_support/core_ext/module/anonymous.rb,
activesupport/lib/active_support/core_ext/module/delegation.rb,
activesupport/lib/active_support/core_ext/module/deprecation.rb,
activesupport/lib/active_support/core_ext/module/method_names.rb,
activesupport/lib/active_support/core_ext/module/remove_method.rb,
activesupport/lib/active_support/core_ext/module/introspection.rb,
activesupport/lib/active_support/core_ext/module/attr_internal.rb,
activesupport/lib/active_support/core_ext/module/synchronization.rb,
activesupport/lib/active_support/core_ext/module/attribute_accessors.rb,
activesupport/lib/active_support/core_ext/module/attr_accessor_with_default.rb

Overview

:nodoc:

Class Attribute Summary collapse

Instance Method Summary collapse

Class Attribute Details

.attr_internal_naming_formatObject

Returns the value of attribute attr_internal_naming_format



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# File 'activesupport/lib/active_support/core_ext/module/attr_internal.rb', line 25

def attr_internal_naming_format
  @attr_internal_naming_format
end

Instance Method Details

#alias_attribute(new_name, old_name) ⇒ Object

Allows you to make aliases for attributes, which includes getter, setter, and query methods.

Example:

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"


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# File 'activesupport/lib/active_support/core_ext/module/aliasing.rb', line 63

def alias_attribute(new_name, old_name)
  module_eval <<-STR, __FILE__, __LINE__ + 1
    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
  STR
end

#alias_method_chain(target, feature) {|aliased_target, punctuation| ... } ⇒ Object

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?, and foo! with the same feature.

Yields:

  • (aliased_target, punctuation)


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# File 'activesupport/lib/active_support/core_ext/module/aliasing.rb', line 23

def alias_method_chain(target, feature)
  # Strip out punctuation on predicates or bang 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, without_method = "#{aliased_target}_with_#{feature}#{punctuation}", "#{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

#anonymous?Boolean

A module may or may not have a name.

module M; end
M.name # => "M"

m = Module.new
m.name # => ""

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 = m          # => m gets a name here as a side-effect
m.name         # => "M"


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# File 'activesupport/lib/active_support/core_ext/module/anonymous.rb', line 19

def anonymous?
  # Uses blank? because the name of an anonymous class is an empty
  # string in 1.8, and nil in 1.9.
  name.blank?
end

#attr_accessor_with_default(sym, default = nil, &block) ⇒ Object

Declare an attribute accessor with an initial default return value.

To give attribute :age the initial value 25:

class Person
  attr_accessor_with_default :age, 25
end

some_person.age
=> 25
some_person.age = 26
some_person.age
=> 26

To give attribute :element_name a dynamic default value, evaluated in scope of self:

attr_accessor_with_default(:element_name) { name.underscore }


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# File 'activesupport/lib/active_support/core_ext/module/attr_accessor_with_default.rb', line 21

def attr_accessor_with_default(sym, default = nil, &block)
  raise 'Default value or block required' unless !default.nil? || block
  define_method(sym, block_given? ? block : Proc.new { default })
  module_eval(<<-EVAL, __FILE__, __LINE__ + 1)
    def #{sym}=(value)                        # def age=(value)
      class << self; attr_reader :#{sym} end  #   class << self; attr_reader :age end
      @#{sym} = value                         #   @age = value
    end                                       # end
  EVAL
end

#attr_internal_accessor(*attrs) ⇒ Object Also known as: attr_internal

Declares an attribute reader and writer backed by an internally-named instance variable.



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# File 'activesupport/lib/active_support/core_ext/module/attr_internal.rb', line 18

def attr_internal_accessor(*attrs)
  attr_internal_reader(*attrs)
  attr_internal_writer(*attrs)
end

#attr_internal_reader(*attrs) ⇒ Object

Declares an attribute reader backed by an internally-named instance variable.



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# File 'activesupport/lib/active_support/core_ext/module/attr_internal.rb', line 3

def attr_internal_reader(*attrs)
  attrs.each do |attr|
    module_eval "def #{attr}() #{attr_internal_ivar_name(attr)} end", __FILE__, __LINE__
  end
end

#attr_internal_writer(*attrs) ⇒ Object

Declares an attribute writer backed by an internally-named instance variable.



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# File 'activesupport/lib/active_support/core_ext/module/attr_internal.rb', line 10

def attr_internal_writer(*attrs)
  attrs.each do |attr|
    module_eval "def #{attr}=(v) #{attr_internal_ivar_name(attr)} = v end", __FILE__, __LINE__
  end
end

#delegate(*methods) ⇒ Object

Provides a delegate class method to easily expose contained objects' methods as your own. Pass one or more methods (specified as symbols or strings) and the name of the target object via the :to option (also a symbol or string). At least one method and the :to option are required.

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

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 delegate object is nil an exception is raised, and that happens no matter whether nil responds to the delegated method. You can get a nil instead with the :allow_nil option.

class Foo
  attr_accessor :bar
  def initialize(bar = nil)
    @bar = bar
  end
  delegate :zoo, :to => :bar
end

Foo.new.zoo   # raises NoMethodError exception (you called nil.zoo)

class Foo
  attr_accessor :bar
  def initialize(bar = nil)
    @bar = bar
  end
  delegate :zoo, :to => :bar, :allow_nil => true
end

Foo.new.zoo   # returns nil


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# File 'activesupport/lib/active_support/core_ext/module/delegation.rb', line 106

def delegate(*methods)
  options = methods.pop
  unless options.is_a?(Hash) && to = options[: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 options[:prefix] == true && options[:to].to_s =~ /^[^a-z_]/
    raise ArgumentError, "Can only automatically set the delegation prefix when delegating to a method."
  end

  prefix = options[:prefix] && "#{options[:prefix] == true ? to : options[:prefix]}_"

  file, line = caller.first.split(':', 2)
  line = line.to_i

  methods.each do |method|
    on_nil =
      if options[:allow_nil]
        'return'
      else
        %(raise "#{self}##{prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}")
      end

    module_eval(<<-EOS, file, line - 5)
      if instance_methods(false).map(&:to_s).include?("#{prefix}#{method}")
        remove_possible_method("#{prefix}#{method}")
      end

      def #{prefix}#{method}(*args, &block)               # def customer_name(*args, &block)
        #{to}.__send__(#{method.inspect}, *args, &block)  #   client.__send__(:name, *args, &block)
      rescue NoMethodError                                # rescue NoMethodError
        if #{to}.nil?                                     #   if client.nil?
          #{on_nil}                                       #     return # depends on :allow_nil
        else                                              #   else
          raise                                           #     raise
        end                                               #   end
      end                                                 # end
    EOS
  end
end

#deprecate(*method_names) ⇒ Object

Declare that a method has been deprecated.

deprecate :foo
deprecate :bar => 'message'
deprecate :foo, :bar, :baz => 'warning!', :qux => 'gone!'


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# File 'activesupport/lib/active_support/core_ext/module/deprecation.rb', line 6

def deprecate(*method_names)
  ActiveSupport::Deprecation.deprecate_methods(self, *method_names)
end

#duplicable?Boolean



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# File 'activesupport/lib/active_support/core_ext/object/duplicable.rb', line 62

def duplicable?
  false
end

#local_constant_namesObject

Returns the names of the constants defined locally rather than the constants themselves. See local_constants.



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# File 'activesupport/lib/active_support/core_ext/module/introspection.rb', line 85

def local_constant_names
  local_constants.map { |c| c.to_s }
end

#local_constantsObject

:nodoc:



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# File 'activesupport/lib/active_support/core_ext/module/introspection.rb', line 78

def local_constants
  inherited = {}

  ancestors.each do |anc|
    next if anc == self
    anc.constants.each { |const| inherited[const] = anc.const_get(const) }
  end

  constants.select do |const|
    !inherited.key?(const) || inherited[const].object_id != const_get(const).object_id
  end
end

#mattr_accessor(*syms) ⇒ Object

Extends the module object with module and instance accessors for class attributes, just like the native attr* accessors for instance attributes.

module AppConfiguration
  mattr_accessor :google_api_key
  self.google_api_key = "123456789"

  mattr_accessor :paypal_url
  self.paypal_url = "www.sandbox.paypal.com"
end

AppConfiguration.google_api_key = "overriding the api key!"


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# File 'activesupport/lib/active_support/core_ext/module/attribute_accessors.rb', line 56

def mattr_accessor(*syms)
  mattr_reader(*syms)
  mattr_writer(*syms)
end

#mattr_reader(*syms) ⇒ Object



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# File 'activesupport/lib/active_support/core_ext/module/attribute_accessors.rb', line 4

def mattr_reader(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
      @@#{sym} = nil unless defined? @@#{sym}

      def self.#{sym}
        @@#{sym}
      end
    EOS

    unless options[:instance_reader] == false
      class_eval(<<-EOS, __FILE__, __LINE__ + 1)
        def #{sym}
          @@#{sym}
        end
      EOS
    end
  end
end

#mattr_writer(*syms) ⇒ Object



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# File 'activesupport/lib/active_support/core_ext/module/attribute_accessors.rb', line 25

def mattr_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
      def self.#{sym}=(obj)
        @@#{sym} = obj
      end
    EOS

    unless options[:instance_writer] == false
      class_eval(<<-EOS, __FILE__, __LINE__ + 1)
        def #{sym}=(obj)
          @@#{sym} = obj
        end
      EOS
    end
  end
end

#parentObject

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


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# File 'activesupport/lib/active_support/core_ext/module/introspection.rb', line 30

def parent
  parent_name ? ActiveSupport::Inflector.constantize(parent_name) : Object
end

#parent_nameObject

Returns the name of the module containing this one.

M::N.parent_name # => "M"


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# File 'activesupport/lib/active_support/core_ext/module/introspection.rb', line 7

def parent_name
  unless defined? @parent_name
    @parent_name = name =~ /::[^:]+\Z/ ? $`.freeze : nil
  end
  @parent_name
end

#parentsObject

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]


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# File 'activesupport/lib/active_support/core_ext/module/introspection.rb', line 47

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

#reachable?Boolean

:nodoc:



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# File 'activesupport/lib/active_support/core_ext/module/reachable.rb', line 5

def reachable? #:nodoc:
  !anonymous? && name.constantize.equal?(self)
rescue NameError
  false
end

#redefine_method(method, &block) ⇒ Object



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# File 'activesupport/lib/active_support/core_ext/module/remove_method.rb', line 7

def redefine_method(method, &block)
  remove_possible_method(method)
  define_method(method, &block)
end

#remove_possible_method(method) ⇒ Object



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# File 'activesupport/lib/active_support/core_ext/module/remove_method.rb', line 2

def remove_possible_method(method)
  remove_method(method)
rescue NameError
end

#synchronize(*methods) ⇒ Object

Synchronize access around a method, delegating synchronization to a particular mutex. A mutex (either a Mutex, or any object that responds to #synchronize and yields to a block) must be provided as a final :with option. The :with option should be a symbol or string, and can represent a method, constant, or instance or class variable. Example:

class SharedCache
  @@lock = Mutex.new
  def expire
    ...
  end
  synchronize :expire, :with => :@@lock
end


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# File 'activesupport/lib/active_support/core_ext/module/synchronization.rb', line 18

def synchronize(*methods)
  options = methods.extract_options!
  unless options.is_a?(Hash) && with = options[:with]
    raise ArgumentError, "Synchronization needs a mutex. Supply an options hash with a :with key as the last argument (e.g. synchronize :hello, :with => :@mutex)."
  end

  methods.each do |method|
    aliased_method, punctuation = method.to_s.sub(/([?!=])$/, ''), $1

    if method_defined?("#{aliased_method}_without_synchronization#{punctuation}")
      raise ArgumentError, "#{method} is already synchronized. Double synchronization is not currently supported."
    end

    module_eval(<<-EOS, __FILE__, __LINE__ + 1)
      def #{aliased_method}_with_synchronization#{punctuation}(*args, &block)     # def expire_with_synchronization(*args, &block)
        #{with}.synchronize do                                                    #   @@lock.synchronize do
          #{aliased_method}_without_synchronization#{punctuation}(*args, &block)  #     expire_without_synchronization(*args, &block)
        end                                                                       #   end
      end                                                                         # end
    EOS

    alias_method_chain method, :synchronization
  end
end