module SingleForwardable

SingleForwardable can be used to setup delegation at the object level as well.

printer =
printer.extend SingleForwardable        # prepare object for delegation
printer.def_delegator "STDOUT", "puts"  # add delegation for STDOUT.puts()
printer.puts "Howdy!"

Also, SingleForwardable can be used to set up delegation for a Class or Module.

class Implementation
  def self.service
    puts "serviced!"

module Facade
  extend SingleForwardable
  def_delegator :Implementation, :service

Facade.service #=> serviced!

If you want to use both Forwardable and SingleForwardable, you can use methods def_instance_delegator and def_single_delegator, etc.

Public Instance Methods

def_delegator(accessor, method, ali = method)
def_delegators(accessor, *methods)
def_single_delegator(accessor, method, new_name=method) click to toggle source

Defines a method method which delegates to accessor (i.e. it calls the method of the same name in accessor). If new_name is provided, it is used as the name for the delegate method. Returns the name of the method defined.

# File forwardable.rb, line 308
def def_single_delegator(accessor, method, ali = method)
  gen = Forwardable._delegator_method(self, accessor, method, ali)

  ret = instance_eval(&gen)
  singleton_class.__send__(:ruby2_keywords, ali) if RUBY_VERSION >= '2.7'
Also aliased as: def_delegator
def_single_delegators(accessor, *methods) click to toggle source

Shortcut for defining multiple delegator methods, but with no provision for using a different name. The following two code samples have the same effect:

def_delegators :@records, :size, :<<, :map

def_delegator :@records, :size
def_delegator :@records, :<<
def_delegator :@records, :map
# File forwardable.rb, line 294
def def_single_delegators(accessor, *methods)
  methods.each do |method|
    next if /\A__(?:send|id)__\z/ =~ method
    def_single_delegator(accessor, method)
Also aliased as: def_delegators
delegate method → accessor
delegate [method, method, ...] → accessor
Alias for: single_delegate
single_delegate [method, method, ...] => accessor click to toggle source

Takes a hash as its argument. The key is a symbol or an array of symbols. These symbols correspond to method names. The value is the accessor to which the methods will be delegated.

# File forwardable.rb, line 273
def single_delegate(hash)
  hash.each do |methods, accessor|
    unless defined?(methods.each)
      def_single_delegator(accessor, methods)
      methods.each {|method| def_single_delegator(accessor, method)}
Also aliased as: delegate