For something that provides the functionality of runtime inheritance
check out the Decorator pattern.
http://www.dofactory.com/Patterns/PatternDecorator.aspx

Essentially the deccorator pattern is like this:
* All decorators conform to the same interface of the object they are
decorating.
* Methods follow this pattern: (In C++)
    type CMyDecorator::SomeMethod(args)
    {
        // Do some additional stuff
        return mObjectBeingDecorated.SomeMethod(args);
    }

The end result is you can add functionality to methods of an object at runtime.

Hope that helps,

-Corey O'Connor

On 9/15/05, David Baelde <david.baelde@gmail.com> wrote:
> Hi list,
> 
> We're getting crazy with some design problem. We need to design a
> buffer object and be able to extend it with some features
> (lexing,color highlighting... yes we're working on an editor). Here's
> the problem.
> 
> I'd like to have a class (or function) for every extension. For
> example be able to write
> new parsed (new lexed (new basic)). I.e. I would need the class:
> 
> class lexed buf =
> object inherit buf method get_token = ... end
> 
> It doesn't work cause inheritance is only from classes, not objects.
> But I want buf to be of any class (any super-class of buffer actually)
> but I don't want to coerce buf to type buffer, cause I want to keep
> extra methods if any were added.
> 
> I'd like to know if there's any simple example of why
> object-inheritance is forbidden, and if any of you have an idea for
> that problem..
> 
> Thanks.
> --
> David
> 
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-- 
-Corey O'Connor