Chris Withers wrote:
Hi All,
I saw the zope.proxies module and wondered if it might be able to help me with two problems I need to solve:
- can these proxies be used to keep track of a traversal path in much the same way (although no seperate containment and context chains needed) as the old Zope 2 acquisition wrappers did?
We generally assign a __parent__ attribute to objects that have a hierarchical parent object. Objects have to explicitly allow this by providing ILocation (or the derived IContained). If they're not ok with having __parent__ assigned, we wrap them in a persistent containment proxy [1]. It will make the original object behave normally, except for the ILocation/IContained API (__parent__, __name__ attributes). It will intercept those values and store them inside the pickled proxy. THat way the object won't ever see the __parent__ attribute assigned to itself.
- once a proxy has been created, the the object it's proxying for be replaced?
I don't understand this question. You'll have to explicitly do the wrapping and then continue to work with the wrapped object. Container implementations use the following kind of code in __setitem__ [2]: if not IContained.providedBy(object): if ILocation.providedBy(object): zope.interface.alsoProvides(object, IContained) else: object = ContainedProxy(object) and then they add 'object' to their datastructure (e.g. a BTree) and assign object.__parent__ and object.__name__. [1] zope.app.container.contained.ContainedProxy [2] zope.app.container.contained.containedEvent