Hi Malcolm, Malcolm Tredinnick wrote: > > class BaseClass(models.Model) : > > final_type = models.ForeignKey(ContentType) > > > > def save(self,*args) : > > For absolute robustness, you should also accept **kwargs here. There are > a couple of places in Django's code that will call save() and pass in > force_insert=True, for example, which won't be handled by *args. In > reality, all you need to be able to handle is force_insert and > force_update, but *args and **kwargs are also pretty useful, > particularly if you aren't doing anything with them except passing them > along.
thanks for the suggestion. What you say is, of course, true. > > self.final_type = > > ContentType.objects.get_for_model(type(self)) > > super(BaseClass,self)save(*args) > > > > def cast(self) : > > return > > self.final_type.get_object_for_this_type(id=self.id) > > > > class DerivedClass(ParentClass) : > > pass > > > > Here is an example: > > > > obj = DerivedClass() > > obj.save() > > > > obj = get_object_or_404(BaseClass, id=3).cast() > > # obj is now of type DerivedClass > > Yes, well done. This looks like the right way to handle this. Glad > somebody's documented it here. Thanks. In principle, I think there is still room for optimization: the database gets hit twice, and it would be sufficient to return only the 'final_type' field in the first call, especially if the base class is voluminous. Since this is possible to do it in SQL, it shouldn't be hard to do it in django, too, but I didn't have time to implement this yet. Cheers, - harold - --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
