module SingleForwardable

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

printer = String.new
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!"
  end
end

module Facade
  extend SingleForwardable
  def_delegator :Implementation, :service
end

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

Alias for: def_single_delegator

def_delegators(accessor, *methods)

Alias for: def_single_delegators

def_single_delegator(accessor, method, new_name=method) Show source

# File lib/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'
  ret
end

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.

Also aliased as: def_delegator

def_single_delegators(accessor, *methods) Show source

# File lib/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)
  end
end

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

Also aliased as: def_delegators

delegate method → accessor

delegate [method, method, ...] → accessor

Alias for: single_delegate

# File lib/forwardable.rb, line 273
def single_delegate(hash)
  hash.each do |methods, accessor|
    unless defined?(methods.each)
      def_single_delegator(accessor, methods)
    else
      methods.each {|method| def_single_delegator(accessor, method)}
    end
  end
end

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.

Also aliased as: delegate

Ruby Core © 1993–2020 Yukihiro Matsumoto
Licensed under the Ruby License.
Ruby Standard Library © contributors
Licensed under their own licenses.