http://docs.djangoproject.com/en/1.2/topics/db/models/#id7
You can access sub-classes with place.restaurant and place.gardenstore if the model has them. I did something similar the other day but added an extra field to parent class to indicate which type of a child model it had (1 for Restaurant etc). I don't know if this is a proper way to handle the situation but it works for me. -Jori On May 18, 7:11 pm, Lee Hinde <leehi...@gmail.com> wrote: > On Tue, May 18, 2010 at 4:27 AM, Jani Tiainen <rede...@gmail.com> wrote: > > > Given the following: > > > > class Place(models.Model): > > > name = models.CharField(max_length=50) > > > address = models.CharField(max_length=80) > > > zip_code = models.CharField(max_length=15) > > > > class Restaurant(Place): > > > serves_hot_dogs = models.BooleanField() > > > serves_pizza = models.BooleanField() > > > > class GardenStore(Place): > > > sells_lady_bugs = models.BooleanField() > > > > and given a query on zip_code in Places, how would I know whether a > > > Place is a Restaurant or a Garden Store? > > > You don't OOTB. > > > I asked same thing quite a while ago - you should be able to find my > > thoughts > > somewhere in this group archives. > > > Rationale behind this is that you're trying to achieve something pretty > > much > > impossible - inheritance in relational world. > > > Thing is that you can have you can really have both: Restaurant and > > GardenStore instance to point to same place - so is that correct case or > > not? > > > Note that "inheritance" is made so that you have relation from Restaurant > > and > > GardenStore tables to Place. There is no simple mechanism to prevent your > > data > > to have references from both "children" to point to "parent". > > > You can have property/method on your model that tries to determine which > > one > > is correct. > > > Or you can re-factor your models (which is usually less painful) so that > > your > > place, provided that it is unique (which actually in this case might not > > be). > > Add simple discriminator field to tell what type of child you must also > > fetch > > to make data complete. > > Thanks Jani; I'd seen some of the older threads, with similar work arounds, > but those discussions pre-dated recent advances. I'll look again for the > thread you mention. > > -- > 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 > athttp://groups.google.com/group/django-users?hl=en. -- 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.
