From: Logan Capaldo <logancapaldo@...>
Date: 2005-12-20T00:21:22+09:00
Subject: Re: TheYAML change the id of Object


On Dec 19, 2005, at 9:10 AM, Andrea wrote:

> I'm using an hash object and i use a Termine Object for the key  
> and, for
> now, a String for the value.
> The class Termine is this:
>
> class Termine
> 	DEFAULT_LANG = "it"
> 	attr_accessor :descrizione
> 	attr_accessor :lingua
> 	def initialize(descrizione="", lingua=DEFAULT_LANG)
> 		@descrizione = descrizione
> 		@lingua = lingua
> 	end
> end
>
> In my test file all is good (compare, edit, delete and reference), but
> if I dump all in a file YAML and then I load the file YAML the equal
> assertion have a failure.
> The attributes 'descrizione' and 'lingua' on the key are the same, but
> the problem is that the id of the object is changed... and so there is
> the failure.
>
>  test_yaml: before hash dump
>  #<Termine:0x2ada6a8>:Key T4 in lingua it -- Value: Definizione uno
>  #<Termine:0x2ada720>:Key T3 in lingua it -- Value: Definizione tre
>  #<Termine:0x2ada750>:Key T2 in lingua it -- Value: Definizione due
>  #<Termine:0x2ada780>:Key T1 in lingua it -- Value: Definizione uno
>
>  test_yaml: after dump (is clear)
>
>  test_yaml: after load
>  #<Termine:0x2ad6400>:Key T4 in lingua it -- Value: Definizione uno
>  #<Termine:0x2ad5f20>:Key T3 in lingua it -- Value: Definizione tre
>  #<Termine:0x2ad5a40>:Key T2 in lingua it -- Value: Definizione due
>  #<Termine:0x2ad5518>:Key T1 in lingua it -- Value: Definizione uno
>
> How can I solve this problem?
>
> Thanks to all for the help...
> --Andrea.
>
> -- 
> Posted via http://www.ruby-forum.com/.
>

You need to overload the == operator and the hash method.

class Termine
    alias eql? ==
    def ==(other)
           descrizione == other.descrizione and lingua == other. lingua
    end
    def hash
         (descrizione + lingua).hash
    end
end

t = Termine.new("Hi")
t2 = Termine.new("Hi")

t == t2 #=> true

h = {}
h[t] = "short hello"
h #=> {#<Termine:0x24a22c @lingua="it", @descrizione="Hi">=>"short  
hello"}
h.has_key?(t2) #=> true