Hi Jean,
The defect I logged is #1424, which is still pending.
http://classic.zope.org:8080/Collector/1434/view
Description:
When you delete a property from a ZClass property sheet, the property is not
actually deleted from **instances** of that ZClass. This leaves properties
lying around where they can be inadvertently acquired, causing problems that
are difficult to trace.
Oddly enough, this related defect was closed "as designed".
http://classic.zope.org:8080/Collector/1652/view
Description:
Deleteing a property from the PropertySheet does not delete the attribute of
any instantiated object of this ZClass. So, the 'property' can still be
accessed(i.e. hasattr(),getattr()), just not changed and can no longer be
deleted because it does not live in the ZClass property Sheet anymore. If a
new instance of the ZClass is created, this 'property' is NOT available as
an attribute.
Response:
As you described, deleting a property from a property sheet does not remove
it from instances. This is correct behavior. It would not be practical to
seek out and modify all instances with the property.
I still think that the issue is a bug that Zope should fix, because it can
play havoc with acquisition and is quite difficult to detect. I remember
spending quite a few puzzled hours before I realized what was
happening...and it could easily happen again. The developer should be
allowed to decide whether or not the full sweep is practical--when a
property is deleted Zope should ask if the ZODB should be swept to fix
zombie instances.
Cheers,
-Paul
-----Original Message-----
From: Jean Jordaan [mailto:jean@upfrontsystems.co.za]
Sent: Wednesday, September 05, 2001 6:30 AM
To: paul@hiringtools.com
Cc: zope@zope.org
Subject: Undead ZClass properties
Hi Paul
I'm writing because I had the same trouble that you describe on
this page:
http://www.zope.org/Members/paulabrams/howto_deleteundeadzclassprops
For the sake of the list, I quote:
I noticed that when you delete a property in a ZClass, it doesn't
actually delete the property in instances of that ZClass! This
leaves zombie properties lying around where they can be
inadvertently acquired, causing problems that are difficult to
trace. Since these properties override properties set in the
REQUEST, if the do get acquired they are difficult to override.
I logged this bug in the collector, which affected my Zope 2.1.6
install. Maik Röder was kind enough to email me the solution below.
He solved the problem by adding this External Method, and calling
all instances with it::
#move_attribute?the_id=abstract
def delete_attribute(self,the_id):
self._delOb(the_id)
On Zope 2.3.3, this gets me::
Error Type: AttributeError
Error Value: _delOb
I tried 'manage_delObjects(ids)' and 'manage_delProperties(ids)',
without success.
I'd like to ask whether you've learnt anything new about this problem
since 2000/12/05? Also, could you tell me what the Issue Id of this
issue is in the collector? I tried searching at
http://classic.zope.org:8080/Collector/
but without success.
Regards,
Jean Jordaan