Module: SingleForwardable

Defined in:
lib/forwardable.rb

Overview

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.

Instance Method Summary collapse

Instance Method Details

#def_single_delegator(accessor, method, ali = method) ⇒ Object Also known as: def_delegator

:call-seq:

def_single_delegator(accessor, method, new_name=method)

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.


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# File 'lib/forwardable.rb', line 305

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

#def_single_delegators(accessor, *methods) ⇒ Object Also known as: def_delegators

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

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# File 'lib/forwardable.rb', line 291

def def_single_delegators(accessor, *methods)
  methods.each do |method|
    next if /\A__(?:send|id)__\z/ =~ method
    def_single_delegator(accessor, method)
  end
end

#single_delegate(hash) ⇒ Object Also known as: delegate

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.

:call-seq:

delegate method => accessor
delegate [method, method, ...] => accessor

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# File 'lib/forwardable.rb', line 270

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