Class: Module

Inherits:
Object show all
Defined in:
activesupport/lib/active_support/core_ext/module/qualified_const.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/object/duplicable.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

Overview

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

– Qualified names are required to be relative because we are extending existing methods that expect constant names, ie, relative paths of length 1. For example, Object.const_get(“::String”) raises NameError and so does qualified_const_get. ++

Class Attribute Summary collapse

Instance Method Summary collapse

Class Attribute Details

.attr_internal_naming_format ⇒ Object

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 21

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"

Returns:

  • (Boolean) 


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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_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 14

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 {|attr_name| attr_internal_define(attr_name, :reader)}
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 8

def attr_internal_writer(*attrs)
  attrs.each {|attr_name| attr_internal_define(attr_name, :writer)}
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 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 =~ /^[^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(<<-EOS, file, line - 2)
        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
      EOS
    else
      exception = %(raise "#{self}##{method_prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}")

      module_eval(<<-EOS, file, line - 1)
        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
      EOS
    end
  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

Modules are not duplicable:

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

Note dup returned the same module object.

Returns:

  • (Boolean) 


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# File 'activesupport/lib/active_support/core_ext/object/duplicable.rb', line 103

def duplicable?
  false
end

#local_constant_names ⇒ Object

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_constants ⇒ Object

: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!"

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.



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# File 'activesupport/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) ⇒ 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 || options[:instance_accessor] == 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 || options[:instance_accessor] == false
      class_eval(<<-EOS, __FILE__, __LINE__ + 1)
        def #{sym}=(obj)
          @@#{sym} = obj
        end
      EOS
    end
  end
end

#parent ⇒ Object

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_name ⇒ Object

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

#parents ⇒ Object

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

#qualified_const_defined?(path, search_parents = true) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'activesupport/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) ⇒ Object 



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# File 'activesupport/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) ⇒ Object 



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# File 'activesupport/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

#reachable? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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

def reachable? #:nodoc:
  !anonymous? && name.safe_constantize.equal?(self)
end

#redefine_method(method, &block) ⇒ Object 



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# File 'activesupport/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) ⇒ Object 



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# File 'activesupport/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) ⇒ 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 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(/([?!=])$/, ''), $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