dozo wrote: > I've run into the following problem with model inheritance, and I > can't find a reasonable way to solve it: > > Let's say I have an Animal model, with a few subclasses: Lion, Tiger, > Zebra and so on. The Animal model is not abstract, because I want to > be able to, say, select all the animals in the database. > > So now I want to go over a collection of animals and determine whether > each one is a Lion or a Tiger (or an Elephant, a Zebra and so on...) > > If I do this: > animals = Animal.objects.all() > I get a list of objects of type Animal. Each one will have a .tiger > attribute or a .lion attribute according to its subclass, so > apparently it "knows" what subclass it belongs to. But I can find no > way of determining its subclass in a generic manner. > > To clarify, I would like to be able to do something like this: > > animals = Animal.objects.all() > for animal in animals: > animal_type = ... > print "I am a", animal_type > > and get: > I am a Zebra > I am a Lion > etc. > > Any ideas? > One way would be to add a "discriminator" column in the base Animal class. The other would be to write a manager that implemented a method that introspected the individual instance attributes. There are probably other ways too.
regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
