From: Harry Ohlsen <harryo@...>
Date: 2002-08-04T22:42:41+09:00
Subject: Re: Detecting when an instance variable is created/set

To give you a feel for what I want to do ...

In the constructor of, say, Album, I'd like something like this, without 
forcing the user to write the "Wrapper.new()"

   class Album
      def initialize(title, songs)
         @title    = Wrapper.new(title)
         @songs = songs.map { |s| Wrapper.new(s) }
      end
   end

Ie, what I want the user to be able to write is

   class Album
      def initialize(title, songs)
         @title    = title
         @songs = songs
      end
   end

Now, if I could catch the "@x = ..." lines I could automate this.

Actually, in my real system, I would only modify what gets stored in @songs, 
not what gets stored in @title, but I have a way to determine whether I need 
to make the conversion.