From: Andrey Kulinich <Andrey.Kulinich@...>
Date: 2003-07-03T17:33:00+09:00
Subject: Re: Auto-serialization (as in Vapor, sql-serialize, etc.): detecting changes to instance variables



Anders Borch wrote:
> I think you should not allow anyone to modify your instance variables 
> without going through your accessor methods. It ruins everything that 
> encapsulation gives you.

Sometimes you can't control modification.

class Session
   attr_accessor :modified
   def initialize
     @data = {}
     @modified = false
   end

   def []( key )
     @data[key]
   end

   def []=( key, value )
     @data[key] = value
     @modified = true
   end
end

session = Session.new
session[:arr] = []
session.modified # true. all ok
session.modified = false

session[:arr].push( 1 )
session.modified # false :(

> Using the method_missing to test if the object has changed after each 
> method call *could* solve your problem. 

There is a trouble with method_missing: you can't redirect methods 
'to_s', '==' and other Object's methods, because they are defined in 
Wrapper.

-- 
with best regards,
Andrey Kulinich
IT Group
Software developer
phone/fax +380 (372) 58-43-10
e-mail: Andrey.Kulinich@itgrp.net
http://www.itgrp.net