From: "David A. Black" <dblack@...>
Date: 2008-10-23T07:09:24+09:00
Subject: Re: subclass a class in the namespace of the that subclass

Hi --

On Thu, 23 Oct 2008, Trans wrote:

> Ever get stuck on a problem, and then after staring at it for way too
> long, get disgusted b/c there is no way to do it the way you need to
> do it, and none of the workable alternatives quite cut it? Well,
> that's been my day.
>
> I know it may seem a bit off the wall. But I want to subclass a class
> that is also defined in the namespace of the subclass. In other words:
>
>  class X < Y
>    class Y
>    end
>  end
>
> Why do I want to do this? Because my library (X) consists of a few
> components, one of them being Y. And I want the end user of the
> library to use it by  typing "X.new". Now, X is all but the same as Y,
> with only with some minor adjustments.
>
> Unfortunately for me there seems to be no way to do this without Ruby
> complaining of a superclass mismatch.

How about this?

c = Class.new
X = Class.new(c)
X.class_eval do
   const_set("Y",c)
end

p X::Y                    # X::Y
p X.superclass            # X::Y
p X.superclass == X::Y    # true

(I used const_set instead of Y = c because that created a top-level
constant.)

I don't know what you need it for but if that helps, there it is :-)


David

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