#12899: Explicitly allow to keep alive objects after deleting related ForeignKey
object instance
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Reporter: rudi | Owner: nobody
Status: new | Milestone: 1.2
Component: Database layer (models, ORM) | Version: 1.2-beta
Keywords: foreignkey, relations | Stage: Unreviewed
Has_patch: 0 |
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Sometimes relation between objects needs to be 'weak': on deleting
'parent' object we should define some 'fallback' keeping 'children'
instanses alive.
It would look like this:
{{{
#!python
class MyModel(Model):
user = ForeignKey(User, blank=True, null=True, weak=True)
}}}
or
{{{
#!python
def get_or_create_default_user(instance):
# some project specific logic here to define
# default user for MyModel instace
# ...
return user
class MyModel(Model):
user = ForeignKey(User, default=get_or_create_default_user, weak=True)
}}}
This will help prevent tricks with signal 'pre_delete' #6870.
Suggested processing of 'weak' relation: just before deleting 'parent' all
related 'weak' relations must be set to default. If 'parent' is the same
as default, then deleting of related objects will occur anyway. If not,
related objects will survive :)
--
Ticket URL: <http://code.djangoproject.com/ticket/12899>
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