# class Module

Extends the API for constants to be able to deal with qualified names. Arguments are assumed to be relative to the receiver.

### Attributes

attr_internal_naming_format[RW]

### Public Instance Methods

alias_attribute(new_name, old_name) click to toggle source

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"

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

alias_method_chain(target, feature) { |aliased_target, punctuation| ... } click to toggle source

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.

    # File 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(%r([?!=])$/, ''), $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?() click to toggle source

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"

    # File 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_internal(*attrs) click to toggle source
Alias for: attr_internal_accessor
attr_internal_accessor(*attrs) click to toggle source

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

    # File lib/active_support/core_ext/module/attr_internal.rb, line 14
    def attr_internal_accessor(*attrs)
      attr_internal_reader(*attrs)
      attr_internal_writer(*attrs)
    end

Also aliased as: attr_internal
attr_internal_reader(*attrs) click to toggle source

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

    # File lib/active_support/core_ext/module/attr_internal.rb, line 3
    def attr_internal_reader(*attrs)
      attrs.each {|attr_name| attr_internal_define(attr_name, :reader)}
    end

attr_internal_writer(*attrs) click to toggle source

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

    # File lib/active_support/core_ext/module/attr_internal.rb, line 8
    def attr_internal_writer(*attrs)
      attrs.each {|attr_name| attr_internal_define(attr_name, :writer)}
    end

delegate(*methods) click to toggle source

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

    # File lib/active_support/core_ext/module/delegation.rb, line 104
      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
        prefix, to, allow_nil = options[:prefix], options[:to], options[:allow_nil]

        if prefix == true && to.to_s =~ %r^[^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

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

        methods.each do |method|
          method = method.to_s

          if allow_nil
            module_eval("          def #{method_prefix}#{method}(*args, &block)        # def customer_name(*args, &block)
                if #{to} || #{to}.respond_to?(:#{method})         #   if client || client.respond_to?(:name)
                  #{to}.__send__(:#{method}, *args, &block)       #     client.__send__(:name, *args, &block)
                end                                               #   end
              end                                                 # end
    ", file, line - 2)
          else
            exception = %Q(raise "#{self}##{method_prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}")

            module_eval("          def #{method_prefix}#{method}(*args, &block)        # def customer_name(*args, &block)
                #{to}.__send__(:#{method}, *args, &block)         #   client.__send__(:name, *args, &block)
              rescue NoMethodError                                # rescue NoMethodError
                if #{to}.nil?                                     #   if client.nil?
                  #{exception}                                    #     # add helpful message to the exception
                else                                              #   else
                  raise                                           #     raise
                end                                               #   end
              end                                                 # end
    ", file, line - 1)
          end
        end
      end

deprecate(*method_names) click to toggle source

Declare that a method has been deprecated.

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

    # File lib/active_support/core_ext/module/deprecation.rb, line 6
    def deprecate(*method_names)
      ActiveSupport::Deprecation.deprecate_methods(self, *method_names)
    end

duplicable?() click to toggle source

Modules are not duplicable:

    m = Module.new # => #<Module:0x10328b6e0>
    m.dup          # => #<Module:0x10328b6e0>

Note `dup` returned the same module object.

    # File lib/active_support/core_ext/object/duplicable.rb, line 103
    def duplicable?
      false
    end

instance_method_names(*args) click to toggle source

    # File lib/active_support/core_ext/module/method_names.rb, line 3
    def instance_method_names(*args)
      instance_methods(*args).map(&:to_s)
    end

local_constant_names() click to toggle source

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

    # File lib/active_support/core_ext/module/introspection.rb, line 85
    def local_constant_names
      local_constants.map { |c| c.to_s }
    end

local_constants() click to toggle source

Returns the constants that have been defined locally by this object and not in an ancestor. This method is exact if running under Ruby 1.9. In previous versions it may miss some constants if their definition in some ancestor is identical to their definition in the receiver.

    # File lib/active_support/core_ext/module/introspection.rb, line 65
    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) click to toggle source

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!"

To opt out of the instance writer method, pass :instance_writer => false. To opt out of the instance reader method, pass :instance_reader => false. To opt out of both instance methods, pass :instance_accessor => false.

    # File lib/active_support/core_ext/module/attribute_accessors.rb, line 60
    def mattr_accessor(*syms)
      mattr_reader(*syms)
      mattr_writer(*syms)
    end

mattr_reader(*syms) click to toggle source

    # File 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("        @@#{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
        end
      end

mattr_writer(*syms) click to toggle source

    # File 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("        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
        end
      end

method_names(*args) click to toggle source

    # File lib/active_support/core_ext/module/method_names.rb, line 7
    def method_names(*args)
      methods(*args).map(&:to_s)
    end

parent() click to toggle source

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

    # File lib/active_support/core_ext/module/introspection.rb, line 30
    def parent
      parent_name ? ActiveSupport::Inflector.constantize(parent_name) : Object
    end

parent_name() click to toggle source

Returns the name of the module containing this one.

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

    # File lib/active_support/core_ext/module/introspection.rb, line 7
    def parent_name
      unless defined? @parent_name
        @parent_name = name =~ %r::[^:]+\Z/ ? $`.freeze : nil
      end
      @parent_name
    end

parents() click to toggle source

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 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

qualified_const_defined?(path) click to toggle source

    # File lib/active_support/core_ext/module/qualified_const.rb, line 27
    def qualified_const_defined?(path)
      QualifiedConstUtils.raise_if_absolute(path)

      QualifiedConstUtils.names(path).inject(self) do |mod, name|
        return unless mod.const_defined?(name)
        mod.const_get(name)
      end
      return true
    end

qualified_const_get(path) click to toggle source

    # File lib/active_support/core_ext/module/qualified_const.rb, line 48
    def qualified_const_get(path)
      QualifiedConstUtils.raise_if_absolute(path)

      QualifiedConstUtils.names(path).inject(self) do |mod, name|
        mod.const_get(name)
      end
    end

qualified_const_set(path, value) click to toggle source

    # File lib/active_support/core_ext/module/qualified_const.rb, line 56
    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

redefine_method(method, &block) click to toggle source

    # File lib/active_support/core_ext/module/remove_method.rb, line 12
    def redefine_method(method, &block)
      remove_possible_method(method)
      define_method(method, &block)
    end

remove_possible_method(method) click to toggle source

    # File lib/active_support/core_ext/module/remove_method.rb, line 2
    def remove_possible_method(method)
      if method_defined?(method) || private_method_defined?(method)
        remove_method(method)
      end
    rescue NameError
      # If the requested method is defined on a superclass or included module,
      # method_defined? returns true but remove_method throws a NameError.
      # Ignore this.
    end

synchronize(*methods) click to toggle source

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

    # File lib/active_support/core_ext/module/synchronization.rb, line 20
      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(%r([?!=])$/, ''), $1

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

          module_eval("        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
    ", __FILE__, __LINE__ + 1)

          alias_method_chain method, :synchronization
        end
      end