ZPatterns-0-4-2a2
When I use an External Attribute Provider, I get an infinite recursion
problem, and Zope hangs.
This is because DataManager (in DataManagers.py) uses normal getattr()
and object.__skinSlot__ methods to get and set the special attribute
__skinSlot__ on DataSkins.
Thus, the system tries to store the __skinSlot__ attribute in the
DataSkin instance by storing the __skinSlot__ attribute in the DataSkin
instance by storing the __skinSlot__ attribute in the DataSkin instance
by...
I can fix this, by patching DataManager to use client.__dict__ instead:
def _readableSlotFor(self,client):
#slot = getattr(client,'__skinSlot__',_marker)
slot = client.__dict__.get('__skinSlot__',_marker)
if slot is _marker: return {}
client._setSlot(slot); return slot
def _writeableSlotFor(self,client):
#slot = getattr(client,'__skinSlot__',_marker)
slot = client.__dict__.get('__skinSlot__',_marker)
if slot is _marker:
#slot = client.__skinSlot__ = PersistentMapping()
slot = client.__dict__['__skinSlot__'] = PersistentMapping()
client._setSlot(slot); return slot
This works, in as far as I can do things like add sub-objects to a
ZClass that derives from DataSkin and ObjectManager without infinite
regress. However, I still get an attribute error. This is because the
External Attribute Provider only offers to set and delete its
attributes. I'm confused as to why this should be -- surely the External
Attribute Provider should offer to get the same attributes as it is
offering to set and delete?
Or, do I have to use an extra provider in the form of some SkinScript or
a Generic Attribute Provider to do the getting?
I tried altering namesForRegistration, so that the External Attribute
Provider would offer to getattr for "*", then refreshed the customizer
I'd put the EAP into.
def namesForRegistration(self,container):
"""XXX"""
return {
'provides':('attributes',),
'setattr': self.Attributes, 'delattr': self.Attributes,
'getattr': self.Attributes
}
I can now add sub-objects to my ZClass instances, and I can traverse to
those sub-objects by typing them into the URL field of my browser.
However, I can't get a list of the sub-objects by calling objectIds.
I'm trying to make sense of External Attribute Provider so that I can
write a BTreeAttributeProvider for DataSkinAddons, as discussed on the
zope-dev list at the end of August, subject "BTreeFolder /w Customizer
support".
Any pointers appreciated.
--
Steve Alexander
Software Engineer
Cat-Box limited
http://www.cat-box.net
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