From: ahoward <ahoward@...>
Date: 2003-05-09T06:14:35+09:00
Subject: state pattern in ruby



rubyists-

when implementing the state pattern/factory in ruby, i have used delegation
before (require 'delegate') and this works well.  however, it seem like
something like this can work just as well - with faster execution times - for
simple cases:

  module M
    class << self
      def new args
	if ...
	  return A.new
	elsif ...
	  return B.new
	else
	  return C.new
	end
      end
    end

  private
    # parent class, perhaps abstract, interface, whatever...
    class M; end

   # delegate classes
    class A < M; end
    class B < M; end
    class C < M; end
  end

allowing

m = M.new args

to return an A, B, or C - all supporting the methods of M::M via inheritence,
interface, abstract inheritence using NotImpliemnted, polymorphism, etc.


any thoughts on this?


-a

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