On Sat, 10 Apr 2004 14:11:56 -0500 <zope@netchan.cotse.net> wrote:
I have the following setup (unrelated lines are omitted):
class Deliverer(Folder): def manage_afterAdd(self, item, container): if item is self: self.__ac_local_roles__ = dr_localroles(self)
class dr_localroles(Persistent): def __init__(self, dr): self.dr = dr
dr_localroles implements a few methods of the dictionary interface, so I can always check the effective settings via the Security/local roles zmi page. In order to computing roles, dr_localroles requires its parent object instance (Deliverer), that's why I store a reference to it as an attribute. Question: - Is there a way for dr_localroles to refer its parent without holding a reference to it or using weak reference?
Yes, use acquisition. Make dr_localroles inherit from Acquisition.Implicit or Acquisition.Explicit.
- Is there an equivalent of sys.getrefcount for ZODB persistent objects?
Cycles like this will not be a problem for ZODB. When either object is deleted it will no longer be reachable from the root, regardless of cycles between them. When the database is packed, unreachable objects are removed.
Also a note for the archives: I wanted to make sure that if I delete a Deliverer object, it will indeed be removed from ZODB.
Once you pack, yes.
For this I got the oid of the object, deleted it and than tried to get it back via the oid. The trick is, that you'll only get a POSKeyError if you pack the database and flush the cache. This latter one was not obvious for me.
Such tricks are not necessary and cause your app to rely too much on the curent implementation of ZODB. Just let the database take care of this for you. In any case, there is a (new) persistent weakref class in ZODB 3.3 which allows you to weakly refer to other persistent objects without causing them to stay in the database like normal references do. -Casey