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? - once a proxy has been created, the the object it's proxying for be replaced? cheers, Chris -- Simplistix - Content Management, Zope & Python Consulting - http://www.simplistix.co.uk
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
P.S.: This is explained in detail in my book, chapter on containers.
Philipp von Weitershausen wrote:
- 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.
Okay, but I'm talking about a context-based chain, ie: keeping track of what objects were traversed through to obtain the current object. Traversed here does *not* mean Zope 3 url traversal which si why I'm looking for something akin to Zope 2's acquisition wrappers, but without the weird containment/context dual wrapping.
- once a proxy has been created, the the object it's proxying for be replaced?
I don't understand this question.
x = proxy(y) a.x = x b.x = x
I now want to do something like:
x.replace(y,z)
...so a and b will still keep their references, but the object being proxied for has been changed. cheers, Chris -- Simplistix - Content Management, Zope & Python Consulting - http://www.simplistix.co.uk
Hi Chris Probably take a look at the z3c.proxy package. This implements a IContainer proxy which will proxy items of a (proxyfied) container. This could give you some ideas how you can proxy items on the fly to your needs. The z3c.proxy package contains a README.txt file with some samples. Also note that you will need the proxy aware copierer and mover if your objects support copy/paste. Regards Roger Ineichen
Betreff: [Zope-dev] Re: proxies
Philipp von Weitershausen wrote:
- 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.
Okay, but I'm talking about a context-based chain, ie: keeping track of what objects were traversed through to obtain the current object. Traversed here does *not* mean Zope 3 url traversal which si why I'm looking for something akin to Zope 2's acquisition wrappers, but without the weird containment/context dual wrapping.
- once a proxy has been created, the the object it's proxying for be replaced?
I don't understand this question.
x = proxy(y) a.x = x b.x = x
I now want to do something like:
x.replace(y,z)
...so a and b will still keep their references, but the object being proxied for has been changed.
cheers,
Chris
-- Simplistix - Content Management, Zope & Python Consulting - http://www.simplistix.co.uk _______________________________________________ Zope-Dev maillist - Zope-Dev@zope.org http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
On Jan 16, 2008, at 3:19 AM, Chris Withers wrote:
Philipp von Weitershausen wrote:
- 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.
Okay, but I'm talking about a context-based chain, ie: keeping track of what objects were traversed through to obtain the current object. Traversed here does *not* mean Zope 3 url traversal which si why I'm looking for something akin to Zope 2's acquisition wrappers, but without the weird containment/context dual wrapping.
Although I'm not quite sure which Zope 2 issue you mean by "the weird containment/context dual wrapping," I suspect that zc.shortcut's traversal proxies do exactly what you want. An old task of mine is to split out this functionality into something like "zc.traversed". But it does what you want, and you don't have to use the shortcuts, and it has the necessary bits for it all to work out. Gary
participants (4)
-
Chris Withers -
Gary Poster -
Philipp von Weitershausen -
Roger Ineichen