Is the m2m_changed() call in the models.py?
Also, it looks indented - if it is, it shouldn't be - in other words -
it doesn't belong to the model.
On Sep 13, 1:27 pm, allyb <beanb...@googlemail.com> wrote:
> I'm finding it difficult to denormalise a field in a django model. I
> have:
>
> class AnswerSet(models.Model):
> title = models.CharField(max_length=255)
> num_answers = models.PositiveIntegerField(editable=False,
> default=0)
> answers = models.ManyToManyField(Answer,
> through='AnswerSetAnswer')
> ...
>
> class AnswerSetAnswer(models.Model):
> answer = models.ForeignKey(Answer)
> answer_set = models.ForeignKey(AnswerSet)
> ...
>
> I want num_answers to contain a count of the number of answers in the
> set.
>
> If 5 answers are initially associated with the AnswerSet "Food" and I
> edit one so it becomes associated with the AnswerSet "Colours", how
> can I recalculate the number of answers in the AnswerSet with "Food"?
> All the signals only seem to send the new data so I can't just
> override the save method.
>
> I've tried using the m2m_changed signal, but it never gets called when
> I edit relationships through the admin form.
>
> Here's my code anyway:
>
> def update_answer_set_num_answers(sender, **kwargs):
> """
> Updates the num_answers field to reflect the number of answers
> associated with this AnswerSet
> """
> print "hello" #
> never gets here
> instance = kwargs.get('instance', False)
>
> print "no instance"
>
> if not instance:
> return
>
> action = kwargs.get('action')
>
> print "action: ", action
>
> if (action != 'pre_remove' and action != 'pre_add' and action !
> = 'clear'):
> return
>
> reverse = kwargs.get('reverse')
>
> if reverse:
> answer_set = instance.answer_set
> else:
> answer_set = instance.answer_set
> num_answers =
> AnswerSetAnswer.objects.filter(answer_set=answer_set.id).count()
>
> if (action == 'pre_remove'):
> num_answers -= int(kwargs.get('pk_set'))
> elif (action == 'pre_add'):
> num_answers += int(kwargs.get('pk_set'))
> elif (action == 'clear'):
> num_answers = 0
>
> answer_set.num_answers = num_answers
>
> print 'n a: ', answer_set.num_answers
> answer_set.save()
>
> m2m_changed.connect(update_answer_set_num_answers, \
> AnswerSet.answers.through)
>
> Setting weak=False or weak=True makes no difference.
>
> How can I get the signal to work?
>
> Thanks
--
You received this message because you are subscribed to the Google Groups
"Django users" group.
To post to this group, send email to django-us...@googlegroups.com.
To unsubscribe from this group, send email to
django-users+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/django-users?hl=en.
