From: Martin DeMello <martindemello@...>
Date: 2003-06-25T22:41:51+09:00
Subject: Re: protect parents from children

Simon Strandgaard <0bz63fz3m1qt3001@sneakemail.com> wrote:
 
> I am sad to hear that. Then I have to learn to live without protection.
> Thanks Guy+Martin for the discussion it has been educational.

You're welcome - it's been educational for me too.

> BTW: Perhaps it could be nice if you could say:
> 
> class A
>  def initialize
>    @value = [1, 2, 3]
>  end
>  subclass_freeze :value      # maybe nice to have ?
> end

This *is* probably hackable, with some judicious delving into Module and
hooks. But you can only freeze an object, not a variable, so it would
prevent @value << [foo] in a subclass, but not @value = bar

As a fellow C++ refugee, I've found that while Ruby doesn't support all
C++'s constructs, there's usually an equivalent way to do any given
problem, and it almost invariably feels better :) 

Actually, I'm still not perfectly clear on what you want. Is it a
variable whose value can be mutated in any methods you write inside
class A, but which client programmers writing classes that inherit from
A can only treat as a constant? How about if they call a method from A
which changes the value of @value? What if they override @initialize and
don't call super - how does the value get set, then? And don't forget
they can simply reopen A and add a method of their own, then call it
from B.

martin