How can I have two foreign keys to the same model in Django?

Question

I want to have two foreign keys to the same model:

class Test(models.model):
    example1 = models.ForeignKey(Example)
    example2 = models.ForeignKey(Example)

I get errors like:

Accessor for field 'example1' clashes with related field 'Example.test_set'. Add a related_name argument to the definition for 'example1'.

Answer 1

Try using related_name:

class Test(models.model):
    example1 = models.ForeignKey('Example', related_name='example1')
    example2 = models.ForeignKey('Example', related_name='example2')

Answer 2

Django uses some python magic to define relationships between models, some of which involves using the name of the models in the relationships (that's where the 'test' in 'test__set' is coming from.) What's happening, I would guess, is that it's trying to put "test__set" in the Example model twice, once for each foreign key you've got defined.

The error message suggests something to try: define a related_name argument (overriding one of those 'test_set's) that it can use instead of autogenerating two clashing names.

More info here

Answer 3

Just do what the error message tells you to do, and if you're unsure what that means, consult the documentation for related_name.