[Grok-dev] Containment with grok.Container

Christian Theune ct at gocept.com
Fri Oct 20 04:25:26 EDT 2006


Philipp von Weitershausen wrote:
> Christian Theune wrote:
>> grok.Container (which derives from
>> zope.app.container.btree.BTreeContainer) does something different than
>> zope.app.folder.Folder.
> Does it? What is it?

Must be something, because the wiki app broke just by switching from the
Folder to the grok.Container. ;) (And no, I don't refer to inconsistent
ZODBs ...)

>> For some reason I had to make the model implement IContained (by
>> subclassing contained.Contained in this case) to get the __parent__
>> attribute set correctly. :/
> Yes, IContained is a way to indicate "please set __parent__ and __name__
> directly on me". Otherwise you'll get a ContainedProxy around the object.
>> This introduced a delicately balanced equilibrium between grok.Model and
>> grok.Container that I'm unhappy with because it depends on the order of
>> the base classes of grok.Model to be able to mix-in models and
>> containers.
> Huh?

The order of 'class Model(Contained, Persistent)' is important if you
mix it in with Container, otherwise Python complains about the MRO.

>> We could argue that grok.Container always is a model and should not be
>> mixed in, or we could try harder to figure out what the BTreeContainer
>> does different that the dependency on Contained is needed.
> Making grok.Container a Model wouldn't be a problem, but perhaps it's
> not a necessity either.

I'm undecided on this too.


gocept gmbh & co. kg - forsterstraße 29 - 06112 halle/saale - germany
www.gocept.com - ct at gocept.com - phone +49 345 122 9889 7 -
fax +49 345 122 9889 1 - zope and plone consulting and development

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