pre_save problem with inherrited model

[iskren]

Hello.

I have a base-class and a child-class. The child-class has a pre_save signal and it has a list of related items to it.
when testing for save action django raises DoesNotExist exception. Traceback follows:

Thank you for the time spent on the Django project

File "../children_pre_save_problem/test_b/tests.py", line 9, in test1_inc_num

invo.save()

File "/usr/lib/pymodules/python2.6/django/db/models/base.py", line 410, in save

self.save_base(force_insert=force_insert, force_update=force_update)

File "/usr/lib/pymodules/python2.6/django/db/models/base.py", line 432, in save_base

signals.pre_save.send(sender=origin, instance=self, raw=raw)

File "/usr/lib/pymodules/python2.6/django/dispatch/dispatcher.py", line 166, in send

response = receiver(signal=self, sender=sender, named)

File "/home/iskren/tc/python/children_pre_save_problem/test_b/models.py", line 30, in invoicedoc_pre_save

instance.recalc_total()

File "/home/iskren/tc/python/children_pre_save_problem/test_b/models.py", line 19, in recalc_total

for item in self.item_set.all():

File "/usr/lib/pymodules/python2.6/django/db/models/fields/related.py", line 324, in get

self.related.model._default_manager.class)

File "/usr/lib/pymodules/python2.6/django/db/models/fields/related.py", line 399, in create_manager

getattr(instance, attname)}

File "/usr/lib/pymodules/python2.6/django/db/models/fields/related.py", line 244, in get

raise self.field.rel.to.DoesNotExist

[iskren]

A Django Program representing the problem, with tests

[iskren]

After creating an empty instance of the Child Class and trying to save it, django DoesNotExist exception;
when the inheritance is removed test works fine. Also if I remove the pre_save it works fine, but the wanted result is not achieved.

[iskren]

The solution I used was to check if the primary key of the instance is None and if so skip the code that breaks.

[Russell Keith-Magee]

A DoesNotExist exception is raised because you're trying to iterate over the obtain and iterate over a list of objects related to an object that has not yet been saved.

If you need more details, please ask on django-users.