From: Tom Sawyer <transami@...>
Date: 2002-08-04T21:49:32+09:00
Subject: Re: Detecting when an instance variable is created/set

On Sun, 2002-08-04 at 06:03, Harry Ohlsen wrote:
> Imagine we have a class like ...
> 
>    class Fred
>       def initialize(a, b)
>          @a = a
>          @b = b
>       end
>    end
> 
> Can I write a method (of class Object or Kernel, perhaps) that will be called 
> when the "@a = a" occurs?  What I'm looking for would be something like ...
> 
>    def instance_var_created(c, name, value)
>       $stderr.puts "@#{name} of class #{c.class} set to #{value}"
>    end
> 
> Is this possible?

this has been touched on in some of the other threads. i brought it up
myself in relation to "automagical" gui bindings. anyway, the short
answer appears to be NO.

since = is not a method you can't redefine it in any way, nor callback
on it. i don't know what your attempting to do, but if you create
accessor methods:

  def a=(x)
    @a = x
  end

then of course you can get at those. but that may not be what you want.

at this point i wish to SPEAK UP and say once again, i would prefer that
EVERYTHING were OO. i choose ruby over python for this very reason!
(although i like ruby over python despite that now anyway). alas not
even ruby is pure.

~transami



> 
> 
-- 
~transami