[Zope3-dev] Re: Constraining where objects can be added

[Philipp von Weitershausen]

Stephan Richter wrote:
> On Sunday 06 June 2004 06:00, Philipp von Weitershausen wrote:
> 
>>Michał Węgrzynek wrote:
>>u 
>>>IArtist.__parent__ = zs.Field(constraint = \
>>>    zcc.ContainerTypesConstraint(IArtistsContainer))
>>
>>This will not work. Interfaces are not classes and they don't expose
>>their fields and method definitions through the getattr protocol, but
>>the getitem protocol. Alas, they don't support the setitem protocol, so
>>there's no good way to dynamically change an interface like.
> 
> See the first chapter of the Content Component part in the Zope 3 book.

Yes, I see you are using setTaggedValue. I think that's a big 
indirection and frankly quite ugly. I would always prefer a separate 
interface, as shown in the buddy demo. I would also think that it is 
easier to understand for newbies, unless you explained how interfaces 
internals (like tagged values) work.

Philipp