From: Paul Brannan <paul@...>
Date: 2001-12-06T23:46:03+09:00
Subject: [ruby-talk:27686] Re: Emulating multimethods

On Thu, Dec 06, 2001 at 01:52:06PM +0900, Christopher S. Kush wrote:
> Now, in CLOS, I could write multimethods and the runtime would
> just handle everything.  But Ruby doesn't have that (yet (hint,
> hint)), so I came up with the following:

I'm not sure if this is quite what you are looking for, but you can
easily get a different function called depending on what state you are
in by using Proc and/or Method objects:

  class Foo
    STATES = { 1 => :foo1, 2 => :foo2, 3 => :foo3 }
  
    def change_state(new_state) 
      @state = new_state
      @foo = method(STATES[new_state])
    end
  
    def initialize; change_state(1); end
    def foo(*args, &block); @foo.call(*args, &block); end
    def foo1; puts "one"; change_state(2); end
    def foo2; puts "two"; change_state(3); end
    def foo3; puts "three"; end
  end
  
  f = Foo.new
  f.foo #=> one
  f.foo #=> two
  f.foo #=> three

Paul