[Zope-dev] Re: Future of ZClasses

[Dieter Maurer]

Philipp von Weitershausen wrote at 2006-9-30 02:30 +0200:
> ...
>> You want to stick this interface to individual objects,
>> while Lennart proposed to stick it to a type and use
>> some kind of inheritance to make it effective on all objects
>> instantiated from this type.
>
>But where does this type come from? Persistent classes are hard (hence 
>ZClasses cannot be maintained by anyone except a few people).

I remember that Jim proposed "PersistentModule"s, currently
a ZODB proposal, to implement functionality similar to ZClasses
in an easier way.

But, I cannot yet answer your question sincerely.

>> For me, Lennart's approach seems to be far more economic, as
>> he does things on an abstract (the type) level rather than
>> always work on the concrete (the individual object) level.
>
>I don't see how introducing another concept (a type) would be more 
>economic.

I find that the introduction of classes with (multiple) inheritance
has been very economic. It was another concept but a highly fruitful
one, despite the fact that they are not so liked in Zope3 land.

As a former mathematician, I also like the introduction of
abstraction layers (object -> type/class -> metatype/metaclass -> ...)
as abstraction often drastically increases economicity.

>It'd be one more thing to worry about wrt persistency etc.

Your answer to Lennart made me a bit unsure.

  It appears as if an interface could live on different
  abstraction levels -- at least together with ZCML and adapter magic.

I am not yet really familiar with this. Let's see what Lennart answers.


-- 
Dieter