Andreas,

You might have a look at: http://spair.swiki.net/21.  This is the
delegation work I did, but it also has an enhanced version of
Hans-Martin Mosner's work on prototypes.  Because I added delegation to
the VM, I was able to enhance his stuff to do instance based multiple
inheritance.

Anyway, you could look at the class ProtoBehavior which does a lot of
what you're talking about.  It is a direct subclass of Behavior...so
it's probably not quite what you're after, but maybe it'll help in some
way.

In general, I'd say the biggest snafu that I encountered was that there
are certain messages that the Squeak environment absolutely requires all
objects to understand (like #nextObject).  These are nicely encapsulated
in ProtoObject however (since you are talking about substitutes for
Metaclass, this should not be an issue for you.).  This drove me nuts
because I wanted to be able to create objects that literally do not
understand anything (including #doesNotUnderstand:) and which used a
Mirror (reflection) to do anything like #instVarAt:, #instVarAt:put:,
#addMethod:, etc.

A ProtoBehavior could inherit behavior from any normal class in the
system...which would be nice for a clean implementation of eToys and
Uniclass behavior in general.  But, unfortunately, it does require the
delegation capability in the VM.

- Stephen

> -----Original Message-----
> From: squeak-dev-admin at lists.squeakfoundation.org 
> [mailto:squeak-dev-admin at lists.squeakfoundation.org] On 
> Behalf Of Andreas Raab
> Sent: Thursday, December 05, 2002 4:17 PM
> To: squeak-dev at lists.squeakfoundation.org
> Subject: Metaclassing
> 
> 
> Hi Guys,
> 
> Has anyone ever tried to provide "Metaclass behavior" by some 
> other class than Metaclass itself?! I have the need for 
> something that is "similar to but not quite the same" as 
> Metaclass' behavior (what I am effectively trying to do is to 
> build a clean representation of Uniclass behavior as in eToys 
> which may require instance ... err ... class ... err ... meta 
> ... oh what the heck, STATE).
> 
> What I am looking for is some primer on how to 
> replace/subclass Metaclass (it drives me nuts just thinking 
> about the fact that a subclass of Metaclass would also be an 
> instance of Metaclass....) and/or any experiences in doing 
> this. In particular little bits like "don't forget to XYZ or 
> else the system will break" would be helpful ;-)
> 
> Cheers,
>   - Andreas
> 
> 
> 
>