Module

alias_attribute(new_name, old_name)

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"

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/aliasing.rb, line 63
63:   def alias_attribute(new_name, old_name)
64:     module_eval "def \#{new_name}; self.\#{old_name}; end          # def subject; self.title; end\ndef \#{new_name}?; self.\#{old_name}?; end        # def subject?; self.title?; end\ndef \#{new_name}=(v); self.\#{old_name} = v; end  # def subject=(v); self.title = v; end\n", __FILE__, __LINE__ + 1
65:   end

alias_method_chain(target, feature)

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.

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/aliasing.rb, line 23
23:   def alias_method_chain(target, feature)
24:     # Strip out punctuation on predicates or bang methods since
25:     # e.g. target?_without_feature is not a valid method name.
26:     aliased_target, punctuation = target.to_s.sub(/([?!=])$/, ''), $1
27:     yield(aliased_target, punctuation) if block_given?
28: 
29:     with_method, without_method = "#{aliased_target}_with_#{feature}#{punctuation}", "#{aliased_target}_without_#{feature}#{punctuation}"
30: 
31:     alias_method without_method, target
32:     alias_method target, with_method
33: 
34:     case
35:       when public_method_defined?(without_method)
36:         public target
37:       when protected_method_defined?(without_method)
38:         protected target
39:       when private_method_defined?(without_method)
40:         private target
41:     end
42:   end

anonymous?()

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"

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/anonymous.rb, line 19
19:   def anonymous?
20:     # Uses blank? because the name of an anonymous class is an empty
21:     # string in 1.8, and nil in 1.9.
22:     name.blank?
23:   end

attr_internal(*attrs)

Alias for attr_internal_accessor

attr_internal_accessor(*attrs)

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

This method is also aliased as attr_internal

Source: show | on GitHub

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

attr_internal_reader(*attrs)

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

Source: show | on GitHub

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

attr_internal_writer(*attrs)

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

Source: show | on GitHub

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

delegate(*methods)

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

Source: show | on GitHub

     # File activesupport/lib/active_support/core_ext/module/delegation.rb, line 104
104:   def delegate(*methods)
105:     options = methods.pop
106:     unless options.is_a?(Hash) && to = options[:to]
107:       raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, :to => :greeter)."
108:     end
109:     prefix, to, allow_nil = options[:prefix], options[:to], options[:allow_nil]
110: 
111:     if prefix == true && to.to_s =~ /^[^a-z_]/
112:       raise ArgumentError, "Can only automatically set the delegation prefix when delegating to a method."
113:     end
114: 
115:     method_prefix =
116:       if prefix
117:         "#{prefix == true ? to : prefix}_"
118:       else
119:         ''
120:       end
121: 
122:     file, line = caller.first.split(':', 2)
123:     line = line.to_i
124: 
125:     methods.each do |method|
126:       method = method.to_s
127: 
128:       if allow_nil
129:         module_eval("def \#{method_prefix}\#{method}(*args, &block)        # def customer_name(*args, &block)\nif \#{to} || \#{to}.respond_to?(:\#{method})         #   if client || client.respond_to?(:name)\n\#{to}.__send__(:\#{method}, *args, &block)       #     client.__send__(:name, *args, &block)\nend                                               #   end\nend                                                 # end\n", file, line - 2)
130:       else
131:         exception = %(raise "#{self}##{method_prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}")
132: 
133:         module_eval("def \#{method_prefix}\#{method}(*args, &block)        # def customer_name(*args, &block)\n\#{to}.__send__(:\#{method}, *args, &block)         #   client.__send__(:name, *args, &block)\nrescue NoMethodError                                # rescue NoMethodError\nif \#{to}.nil?                                     #   if client.nil?\n\#{exception}                                    #     # add helpful message to the exception\nelse                                              #   else\nraise                                           #     raise\nend                                               #   end\nend                                                 # end\n", file, line - 1)
134:       end
135:     end
136:   end

deprecate(*method_names)

Declare that a method has been deprecated.

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

Source: show | on GitHub

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

duplicable?()

Modules are not duplicable:

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

Note dup returned the same module object.

Source: show | on GitHub

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

instance_method_names(*args)

Source: show | on GitHub

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

local_constant_names()

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

Source: show | on GitHub

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

local_constants()

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.

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/introspection.rb, line 65
65:     def local_constants
66:       inherited = {}
67: 
68:       ancestors.each do |anc|
69:         next if anc == self
70:         anc.constants.each { |const| inherited[const] = anc.const_get(const) }
71:       end
72: 
73:       constants.select do |const|
74:         !inherited.key?(const) || inherited[const].object_id != const_get(const).object_id
75:       end
76:     end

mattr_accessor(*syms)

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.

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/attribute_accessors.rb, line 64
64:   def mattr_accessor(*syms)
65:     mattr_reader(*syms)
66:     mattr_writer(*syms)
67:   end

mattr_reader(*syms)

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/attribute_accessors.rb, line 4
 4:   def mattr_reader(*syms)
 5:     options = syms.extract_options!
 6:     syms.each do |sym|
 7:       class_eval("@@\#{sym} = nil unless defined? @@\#{sym}\n\ndef self.\#{sym}\n@@\#{sym}\nend\n", __FILE__, __LINE__ + 1)
 8: 
 9:       unless options[:instance_reader] == false || options[:instance_accessor] == false
10:         class_eval("def \#{sym}\n@@\#{sym}\nend\n", __FILE__, __LINE__ + 1)
11:       end
12:     end
13:   end

mattr_writer(*syms)

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/attribute_accessors.rb, line 27
27:   def mattr_writer(*syms)
28:     options = syms.extract_options!
29:     syms.each do |sym|
30:       class_eval("def self.\#{sym}=(obj)\n@@\#{sym} = obj\nend\n", __FILE__, __LINE__ + 1)
31: 
32:       unless options[:instance_writer] == false || options[:instance_accessor] == false
33:         class_eval("def \#{sym}=(obj)\n@@\#{sym} = obj\nend\n", __FILE__, __LINE__ + 1)
34:       end
35:     end
36:   end

method_names(*args)

Source: show | on GitHub

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

parent()

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

Source: show | on GitHub

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

parent_name()

Returns the name of the module containing this one.

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

Source: show | on GitHub

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

parents()

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]

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/introspection.rb, line 47
47:   def parents
48:     parents = []
49:     if parent_name
50:       parts = parent_name.split('::')
51:       until parts.empty?
52:         parents << ActiveSupport::Inflector.constantize(parts * '::')
53:         parts.pop
54:       end
55:     end
56:     parents << Object unless parents.include? Object
57:     parents
58:   end

qualified_const_defined?(path)

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/qualified_const.rb, line 27
27:     def qualified_const_defined?(path)
28:       QualifiedConstUtils.raise_if_absolute(path)
29: 
30:       QualifiedConstUtils.names(path).inject(self) do |mod, name|
31:         return unless mod.const_defined?(name)
32:         mod.const_get(name)
33:       end
34:       return true
35:     end

qualified_const_defined?(path, search_parents=true)

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/qualified_const.rb, line 37
37:     def qualified_const_defined?(path, search_parents=true)
38:       QualifiedConstUtils.raise_if_absolute(path)
39: 
40:       QualifiedConstUtils.names(path).inject(self) do |mod, name|
41:         return unless mod.const_defined?(name, search_parents)
42:         mod.const_get(name)
43:       end
44:       return true
45:     end

qualified_const_get(path)

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/qualified_const.rb, line 48
48:   def qualified_const_get(path)
49:     QualifiedConstUtils.raise_if_absolute(path)
50: 
51:     QualifiedConstUtils.names(path).inject(self) do |mod, name|
52:       mod.const_get(name)
53:     end
54:   end

qualified_const_set(path, value)

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/qualified_const.rb, line 56
56:   def qualified_const_set(path, value)
57:     QualifiedConstUtils.raise_if_absolute(path)
58: 
59:     const_name = path.demodulize
60:     mod_name = path.deconstantize
61:     mod = mod_name.empty? ? self : qualified_const_get(mod_name)
62:     mod.const_set(const_name, value)
63:   end

redefine_method(method, &block)

Source: show | on GitHub

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

remove_possible_method(method)

Source: show | on GitHub

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

synchronize(*methods)

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

Source: show | on GitHub

    # File activesupport/lib/active_support/core_ext/module/synchronization.rb, line 20
20:   def synchronize(*methods)
21:     options = methods.extract_options!
22:     unless options.is_a?(Hash) && with = options[:with]
23:       raise ArgumentError, "Synchronization needs a mutex. Supply an options hash with a :with key as the last argument (e.g. synchronize :hello, :with => :@mutex)."
24:     end
25: 
26:     methods.each do |method|
27:       aliased_method, punctuation = method.to_s.sub(/([?!=])$/, ''), $1
28: 
29:       if method_defined?("#{aliased_method}_without_synchronization#{punctuation}")
30:         raise ArgumentError, "#{method} is already synchronized. Double synchronization is not currently supported."
31:       end
32: 
33:       module_eval("def \#{aliased_method}_with_synchronization\#{punctuation}(*args, &block)     # def expire_with_synchronization(*args, &block)\n\#{with}.synchronize do                                                    #   @@lock.synchronize do\n\#{aliased_method}_without_synchronization\#{punctuation}(*args, &block)  #     expire_without_synchronization(*args, &block)\nend                                                                       #   end\nend                                                                         # end\n", __FILE__, __LINE__ + 1)
34: 
35:       alias_method_chain method, :synchronization
36:     end
37:   end

Class Module < Object