Question

Basically, I have a model where I’ve created a superclass that many other classes share, and then each of those classes has some unique features that differ from each other. Let’s say class A is the superclass, and class B, C, and D are children of that class.

Both class B and class C can have multiples of class D, however I’ve seen that it’s best to put the foreign key relationship in class D, which then refers to its parent class. Now in other languages, I could simply say it has a ForeignKey relationship to class A, and then the language recognizes the classes’ true type. However, I don’t think that’s how it works with Python.

What’s the best recommended way of pursuing this issue?

EDIT: Here is roughly what I mean…

class A(models.Model):
    field = models.TextField()

class B(A):
    other = <class specific functionality>

class C(A):
    other2 = <different functionality>

class D(A):
    #I would like class D to have a foreign key to either B or C, but not both.

Essentially, class B and class C both have multiple class D’s. But a particular class D only belongs to one of them.

Answer 1

From the Django Docs:

For example, if you were building a
database of “places”, you would build
pretty standard stuff such as address,
phone number, etc. in the database.
Then, if you wanted to build a
database of restaurants on top of the
places, instead of repeating yourself
and replicating those fields in the
Restaurant model, you could make
Restaurant have a OneToOneField to
Place (because a restaurant “is a”
place; in fact, to handle this you’d
typically use inheritance, which
involves an implicit one-to-one
relation).

Normally, you would just have Restaurant inherit from Place. Sadly, you need what I consider a hack: making a one-to-one reference from subclass to superclass (Restaurant to Place)