Question

Sorry for the none-descriptive title, but I didn’t really have a clue as to how to word this.

Say I have two models as such:

class Person(...):
  name = ... #have an attribute

class Family(...):
  mum = models.OneToOneField(Person)
  dad = models.OneToOneField(Person)

When I have a family containing mum and dad, I would think calling dad.family would yield me the family dad is in. However, I get an error message saying that this clashes with the mum attribute. The solution here is to use relative_names. But calling the family from mums side something else than from dads feels weird for me. WHy can’t I just call dad.family? Could someone explain to me what exactly is clashing here?

Thanks!

Answer 1

The problem is that, given your model, a Person could be a mum to one Family, and a dad to a different family.

In that case, a query like this would be ambiguous:

pat = Person.objects.get(name='Pat')
family1.mum = pat
family1.save()

family2.dad = pat
family2.save()

pat.family # Which family do we want?

For that reason, you need to define a reverse relation name for each one (family_as_mum and family_as_dad, for instance)