Forwarding when subclassing is not possible...

[Roger M. Burkhart]

Benedikt Stefansson writes:

> I've been wanting to implement this for a long time, but now I found a
> pressing reason. I'd like to subclass from List, but according to
> Roger's documentation that is not yet allowed. But he hints at the fact
> that forwarding might solve the problem:

Actually, there are people who do this subclassing (not from List itself,
but from one of the List implementation classes, typically List_linked), but
this method of subclassing will change somewhat in the next major release
(later this fall), so for the time being it's not recommended if you can
avoid it.

Forwarding of messages has been discussed on the swarm-support archive;
see particularly the thread of messages starting at:
  www.santafe.edu/projects/swarm/archive/list-archive.9702/index.html#184

The NSInvocation is a newer NextStep method of doing message forwarding,
while gcc uses an older approach that doesn't involve a separate invocation
object.  Be sure to note Scott Christley's warnings about machine-specific
problems in the above-referenced thread.  As far as I know we still don't
have complete machine support of the basic Objective C dynamic invocation
features in the production releases of gcc.

--Roger



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