Class: Module

Inherits:
Object show all
Includes:
ActiveSupport::Deprecation::ClassMethods
Defined in:
lib/active_support/dependencies.rb,
lib/active_support/deprecation.rb,
lib/active_support/core_ext/module/loading.rb,
lib/active_support/core_ext/module/aliasing.rb,
lib/active_support/core_ext/module/inclusion.rb,
lib/active_support/core_ext/module/delegation.rb,
lib/active_support/core_ext/module/attr_internal.rb,
lib/active_support/core_ext/module/introspection.rb,
lib/active_support/vendor/builder-2.1.2/blankslate.rb,
lib/active_support/core_ext/module/attribute_accessors.rb,
lib/active_support/core_ext/module/attr_accessor_with_default.rb

Overview

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

Instance Method Summary collapse

Methods included from ActiveSupport::Deprecation::ClassMethods

#deprecate, #deprecated_method_warning, #deprecation_horizon

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 '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 #{new_name}?; self.#{old_name}?; end
    def #{new_name}=(v); self.#{old_name} = 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 '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

#append_features(mod) ⇒ Object 



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# File 'lib/active_support/vendor/builder-2.1.2/blankslate.rb', line 105

def append_features(mod)
  result = blankslate_original_append_features(mod)
  return result if mod != Object
  instance_methods.each do |name|
    BlankSlate.hide(name)
  end
  result
end

#as_load_path ⇒ Object 



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

def as_load_path
  if self == Object || self == Kernel
    ''
  elsif is_a? Class
    parent == self ? '' : parent.as_load_path
  else
    name.split('::').collect do |word|
      word.underscore
    end * '/'
  end
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 '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__)
    def #{sym}=(value)
      class << self; attr_reader :#{sym} end
      @#{sym} = value
    end
  EVAL
end

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

Declare attributes backed by ‘internal’ instance variables names.



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# File 'lib/active_support/core_ext/module/attr_internal.rb', line 17

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

#attr_internal_reader(*attrs) ⇒ Object

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



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# File '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"
  end
end

#attr_internal_writer(*attrs) ⇒ Object

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



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# File '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"
  end
end

#blankslate_original_append_features ⇒ Object 



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# File 'lib/active_support/vendor/builder-2.1.2/blankslate.rb', line 104

alias blankslate_original_append_features append_features

#const_missing(class_id) ⇒ Object

Use const_missing to autoload associations so we don’t have to require_association when using single-table inheritance.



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# File 'lib/active_support/dependencies.rb', line 452

def const_missing(class_id)
  Dependencies.load_missing_constant self, class_id
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 as the final :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 the variable as a symbol:

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



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# File 'lib/active_support/core_ext/module/delegation.rb', line 48

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

  methods.each do |method|
    module_eval(<<-EOS, "(__DELEGATION__)", 1)
      def #{method}(*args, &block)
        #{to}.__send__(#{method.inspect}, *args, &block)
      end
    EOS
  end
end

#included_in_classes ⇒ Object 



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

def included_in_classes
  classes = []
  ObjectSpace.each_object(Class) { |k| classes << k if k.included_modules.include?(self) }

  classes.reverse.inject([]) do |unique_classes, klass| 
    unique_classes << klass unless unique_classes.collect { |k| k.to_s }.include?(klass.to_s)
    unique_classes
  end
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 'lib/active_support/core_ext/module/introspection.rb', line 38

def local_constant_names
  local_constants.map(&:to_s)
end

#local_constants ⇒ Object

Return the constants that have been defined locally by this object and not in an ancestor. This method may miss some constants if their definition in the ancestor is identical to their definition in the receiver.



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

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 



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# File 'lib/active_support/core_ext/module/attribute_accessors.rb', line 44

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

#mattr_reader(*syms) ⇒ Object

:nodoc:



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

def mattr_reader(*syms)
  syms.each do |sym|
    next if sym.is_a?(Hash)
    class_eval(<<-EOS, __FILE__, __LINE__)
      unless defined? @@#{sym}
        @@#{sym} = nil
      end
      
      def self.#{sym}
        @@#{sym}
      end

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

#mattr_writer(*syms) ⇒ Object 



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

def mattr_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__)
      unless defined? @@#{sym}
        @@#{sym} = nil
      end
      
      def self.#{sym}=(obj)
        @@#{sym} = obj
      end
      
      #{"
      def #{sym}=(obj)
        @@#{sym} = obj
      end
      " unless options[:instance_writer] == false }
    EOS
  end
end

#parent ⇒ Object

Return the module which contains this one; if this is a root module, such as ::MyModule, then Object is returned.



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

def parent
  parent_name = name.split('::')[0..-2] * '::'
  parent_name.empty? ? Object : parent_name.constantize
end

#parents ⇒ Object

Return all the parents of this module, ordered from nested outwards. The receiver is not contained within the result.



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# File 'lib/active_support/core_ext/module/introspection.rb', line 11

def parents
  parents = []
  parts = name.split('::')[0..-2]
  until parts.empty?
    parents << (parts * '::').constantize
    parts.pop
  end
  parents << Object unless parents.include? Object
  parents
end

#rails_original_const_missing ⇒ Object

Rename the original handler so we can chain it to the new one



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# File 'lib/active_support/dependencies.rb', line 448

alias :rails_original_const_missing :const_missing

#unloadable(const_desc = self) ⇒ Object 



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# File 'lib/active_support/dependencies.rb', line 456

def unloadable(const_desc = self)
  super(const_desc)
end