python - How to specify Parent-Child relationship within one Model?

Question

For example I have following code:

class FamilyMember(models.Model):
    user = models.OneToOneField(User)

And I have following situations:

a1 = FamilyMember.objects.get(id=1)
a1.first_name = 'John'
a1.last_name = 'Smith'
(a1 is a parent of a2)

a2 = FamilyMember.objects.get(id=2)
a2.first_name = 'Mark'
a2.last_name = 'Smith'
(a2 is a child of a1 and parent of a3 in the same time)

a3 = FamilyMember.objects.get(id=3)
a3.first_name = 'Jason'
a3.last_name = 'Smith'
(a3 is a child of a2)

How can i accomplish that kind of relationships within one model ?

Answer 1

You can do this with a simple ForeignKey to self to indicate the parent:

parent = models.ForeignKey('self', blank=True, null=True, related_name='children')

Now you can do a2.parent = a1, and will automatically get access to a1.children.all().