[Zope3-dev] Containment constraints

[Jim Fulton]

Roché Compaan wrote:
> The containment constraints are yummy. Just one thing I am concerned
> about is that the current implementation (__setitem__.precondition on an
> Interface) may lead to a lot of dead chickens. I seem to be ending up
> with a lot of interfaces that only subclass IContainer and set
> preconditions.

Yes, and likewise for the __parent__ constraint.

> Add to that the class implementation and ZCML one has to
> write for each interface and the dead chickens start to smell.

The zcml one has to write?  I don't follow this.

> Should I just get used to it or am I missing some zen.

Well, this is new. We need to get some experience.  I'm sure
it can be improved.  I'll note that implementing containers is
now *much* simpler than it used to be.

(In fact, I really need to update the slided, because, at the
  Bangalore sprint a new zcml directive was added that vastly
  simplifies defining the contents, add and index pages.)

I suspect that a zcml directive and/or Python api could automate
certain aspects of defining these interfaces. Proposals are welcome.

Jim

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