From: ara.t.howard@...
Date: 2007-03-21T04:44:13+09:00
Subject: Re: Defining my own class of unique objects

On Wed, 21 Mar 2007, jmay wrote:

> Hi-
>
> I'm trying to define a class with semantics similar to Fixnum, where every
> object is unique.  Each object has some internal state, more complex that a
> single numeric value.  Also, I want this to work across marshalling and
> YAML.load.  Semantics like this:
>
> Foo.new("stuff").object_id == Foo.new("stuff").object_id

you can do this using

   http://raa.ruby-lang.org/project/multiton/

or write your own based on

   http://en.wikipedia.org/wiki/Multiton_pattern

> Foo.new("stuff").object_id == YAML.load(Foo.new("stuff").to_yaml).object_id

dunno the yaml semantics, but this marshal example shows the pattern you will
need to follow using mashaling as an example:

   harp:~ > cat a.rb
   require 'multiton'

   class Unique
     include Multiton
     def initialize *args
       @args = args
     end

     def _dump *a
       Marshal.dump @args, *a
     end

     def self._load buf
       instance *(Marshal.load(buf))
     end
   end

   p( Unique.instance(1,2).object_id == Unique.instance(1,2).object_id )
   p( Unique.instance(1,2).object_id == Marshal.load(Marshal.dump(Unique.instance(1,2))).object_id )


   harp:~ > ruby a.rb
   true
   true

regards.

-a
-- 
be kind whenever possible... it is always possible.
- the dalai lama