I've settled on a solution for this now which works fine. So I'm overriding the delete function for my model. In that function I'm clearing any references that I need to but I'm then also calling delete manually on any child objects that I also have overridden delete functions for. This does require an extra step to manually call delete again on child objects but at least it means I can have delete logic in a sensible place.
Also found this article on the net which details the options for this problem nicely http://stackoverflow.com/questions/2475249/what-are-the-options-for-overriding-djangos-cascading-delete-behaviour On Apr 13, 7:49 pm, cootetom <coote...@gmail.com> wrote: > OK I've tried the pre_delete approach but unfortunately it doesn't > work for what I'm trying here. It appears that django gets a > collection of objects that it is going to delete then it calls > pre_delete on each object before finally deleting the objects. So > django has decided which objects to delete way before the pre_delete > function is called meaning if I do a clear inside that function it > makes no difference to the list of objects that will be deleted. > > At the moment the only approach I can think of is to define functions > for deleting models and do the clear logic before calling delete. This > seems really ugly to me but I can't see any other way. > > def deleteModal2(obj): > obj.related_model.clear() > obj.delete() > > def deleteModal1(obj): > for childObj in obj.related_model.all(): > deleteModal2(childObj) > > obj.related_model.clear() > obj.delete() > > Any more ideas? > > On Apr 13, 9:29 am, cootetom <coote...@gmail.com> wrote: > > > > > Thanks Ian, > > > I'll give that a go later. I don't suppose it matters what order they > > are called in because it's only clearing references to do with the > > model instance it's calling from. > > > On Apr 13, 2:15 am, Ian Lewis <ianmle...@gmail.com> wrote: > > > > Tom, > > > > You could try doing this clear logic in a pre_delete signal. You might > > > have > > > to test out the timing of when the signals get called but it should call > > > pre_delete for all deleted models. In this case it would call pre_delete > > > on > > > model2 before model1 but you should be able to get what you are looking > > > for. > > > >http://docs.djangoproject.com/en/dev/ref/signals/#pre-delete > > > > On Tue, Apr 13, 2010 at 8:21 AM, cootetom <coote...@gmail.com> wrote: > > > > Hi, I'm trying to figure out the way django deletes models so that I > > > > can clear the correct references that I need to prior to deleting. So > > > > I have models set up with overrided delete functions so that I can do > > > > clears before the actual delete. However, it appears the delete > > > > functions in a model don't get called in the cascade of deletes so not > > > > each child model gets to do it's clear of linked data before > > > > deleting. > > > > > def model1(models.Model): > > > > def delete(self): > > > > self.related_model.clear() > > > > super(model1, self).delete() > > > > > def model2(models.Model): > > > > model2 = models.ForeignKey(model2) > > > > > def delete(self): > > > > self.another_related_model.clear() > > > > super(model2, self).delete() > > > > > So if I do model1.delete() then it will do it's clear but it appears > > > > it won't do the clear from model2? Am I getting this behaviour right > > > > or am I doing something wrong here? > > > > > The model class seems like the best place to put delete logic in so > > > > that when it's deleted it clears any data it needs to first. > > > > > - Tom > > > > > -- > > > > 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<django-users%2bunsubscr...@google > > > > groups.com> > > > > . > > > > For more options, visit this group at > > > >http://groups.google.com/group/django-users?hl=en. > > > > -- > > > ======================================= > > > 株式会社ビープラウド イアン・ルイス > > > 〒150-0021 > > > 東京都渋谷区恵比寿西2-3-2 NSビル6階 > > > email: ianmle...@beproud.jp > > > TEL:03-6416-9836 > > > FAX:03-6416-9837http://www.beproud.jp/ > > > ======================================= -- 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.
