From: dblack@...
Date: 2002-09-06T11:45:14+09:00
Subject: Re: Ruby aesthetics

Hi --

On Fri, 6 Sep 2002, Albert Wagner wrote:

> On Thursday 05 September 2002 12:08 pm, Christian Szegedy wrote:
> <snip>
> > What I really dislike in Ruby, that the data members are seen
> > by the child classes. This is a very serious issue, and a claer
> > violation of object-orientation.
> >
> > I think Ruby would be a much better language if the instance
> > variables would only live per class and not per hierarchy...
> >
>
> I don't understand what is bad about this.  I typically depend on instance
> variables in the parent(s) being directly accesssible.

I think I understand the objection (thanks in large part to Holden's
explaining it to me on irc).  As I understand it, the problem is that
if you do this:

  class A
    def initialize(x)
      @thing = x
    end

    def talk
      puts "My thing is #{@thing}."
    end
  end

  class B < A
    def talk
      puts "I have a thing which is #{@thing}."
    end
  end

and then class A is rewritten so that @thing is renamed to @item, B
will break.

I've tended to see instance variables as part of the... well, I was
going to say the interface, but that's wrong... part of the stuff
you're allowed to know about.  But I'm seeing that that's pretty
non-robust.


David

-- 
David Alan Black                      | Register for RubyConf 2002!
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