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.


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# File 'lib/forwardable.rb', line 277

def def_single_delegator(accessor, method, ali = method)
  accessor = accessor.to_s
  if method_defined?(accessor) || private_method_defined?(accessor)
    accessor = "#{accessor}()"
  end

  line_no = __LINE__; str = %{
    def #{ali}(*args, &block)
      begin
        #{accessor}.__send__(:#{method}, *args, &block)
      rescue ::Exception
        [email protected]_if{|s| ::Forwardable::FILE_REGEXP =~ s} unless ::Forwardable::debug
        ::Kernel::raise
      end
    end
  }

  instance_eval(str, __FILE__, line_no)
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 263

def def_single_delegators(accessor, *methods)
  methods.delete("__send__")
  methods.delete("__id__")
  for method in methods
    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 243

def single_delegate(hash)
  hash.each{ |methods, accessor|
    methods = [methods] unless methods.respond_to?(:each)
    methods.each{ |method|
      def_single_delegator(accessor, method)
    }
  }
end