From: Trans <transfire@...>
Date: 2008-10-23T11:21:55+09:00
Subject: Re: subclass a class in the namespace of the that subclass



On Oct 22, 6:09 pm, "David A. Black" <dbl...@rubypal.com> wrote:
> 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.)

(see my response to the Captain)

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

Ok. Well I'll spill... I've been working on an "uber" commandline
parser:

  class Usage < Command
    class Command
    class Option
    class Argument

Thus Usage is the main toplevel command. A command can have
subcommands, options, arguments... so forth and so on.

T.