From: Joel VanderWerf <vjoel@...>
Date: 2006-12-20T04:37:24+09:00
Subject: Re: compare two objects without take its ID in consideration

Lobosque Lucas wrote:
> Is there a way to compare two objects without take its ID in
> consideration? For example:
> 
> #<Game_Esper:0xdcc7e0 @str=6, @mdfel = 0, @name = "Ifrit"> ==
> #<Game_Esper:0xeda51e @str=6, @mdfel = 0, @name = "Ifrit">
> 
> It'll return false, because the object ID is different. But i want it to
> return true, because the arguments (is it the right name?) are all
> equal.

This is one pattern I use, and (because it defines #eql? and #hash) it 
also gives you the hashing behavior you will probably want to go with it:

   module ContentEquality
     def hash
       content.hash
     end

     def eql?(other)
       other.class == self.class and content.eql? other.content
     end

     def ==(other)
       other.class == self.class and content == other.content
     end
   end

   class Game
     include ContentEquality
     def initialize str, mdfel, name
       @str, @mdfel, @name = str, mdfel, name
     end

     def content
       [@str, @mdfel, @name]
     end
   end

   g1 = Game.new "foo", "bar", "baz"
   g2 = Game.new "foo", "bar", "baz"

   p g1 == g2 # ==> true

   h = {}
   h[g1] = true
   p h[g2] # ==> true


-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407