From: Jan Svitok <jan.svitok@...>
Date: 2006-08-29T23:59:11+09:00
Subject: Re: Extending class from other module

On 8/29/06, Alexander Rysenko <rysenko@gmail.com> wrote:
> 1st question: If I got it right, modules in Ruby can be used as
> namespaces. Is it ok? Is there some other (preffered) way?

Exactly. Look for example at test/unit[1], or rails[2] as they contain
a lot of classes divided into modules for namespace separation.

> 2nd question: I need to extend some class from one module in another
> one. Basically I do something like this:
>
> module Mod1
>   class A1
>   end
>
>   class B2 < Mod2::B1
>   end
> end
>
> module Mod2
>   class B1
>   end
> end
>
> But this doesn't really work (seems like B1 isn't really found). How can
> I do such a thing?

The problem is in the order of evaluation. Install rcov (gem install
rcov) and see for yourself what lines ruby has read already and what
not.

I guess the problem is that B1 is not known to ruby yet. You can fix
that by reversing the order, or just declaring the class without any
content:

module Mod2
   class B1
   end
end

module Mod1
   class B2 < Mod2::B1
      def xxx...
...
      end
   end
end

module Mod2
   class B1
     def yyy
...
     end
   end
end

I don't have ruby installed now, so I can't verify these things, so
please take it as such.

[1] http://ruby-doc.org/stdlib/libdoc/test/unit/rdoc/index.html
[2] http://api.rubyonrails.com/