On 07/26/2016 02:29 PM, drMental wrote:
I'd like to restrict deletion and updates on an object based on the
boolean attribute 'locked' on the same object.
I've managed to successfully suppress updates but it doesn't seem to
work for deletes with the following code.
@listen_for(mapper, 'mapper_configured')
def mapper_configured(mapper, cls):
def extract(obj):
try: return obj[0]
except IndexError: return False
if issubclass(cls, Base):
@listen_for(cls, 'before_update)
@listen_for(cls, 'before_delete)
def restrict(mapper, connection, target):
session = Session.object_session(target)
added, unchanged, deleted = map(extract,
inspect(target).attrs.locked.history)
if unchanged:
session.expire(target)
How can I make SA restrict the delete and keep object in database when a
session.delete(obj) is issued?
if you want to raise an error, super easy. raise it in the
before_update and before_delete events.
if you want to make the changes be silently reset, that is probably
better done inside of the before_flush() events; that way, the object is
not considered for the flush plan at all. resetting it inside the
mapper event would probably cause problems (I guess with delete it's
still deleting it).
But even then, if an object has a "locked" state, I would probably do
this at the object level; as soon as "locked" is set, call
session.expire() and/or session.refresh() so it has state right there,
and then override __setattr__() to block all subsequent activities
during that locked state. Then keep before_update and before_delete
in, and have them raise; since no object should ever get in there with
locked + pending changes they serve as assertions.
Any help appreciated,
Mats
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