AttributeError: 'User' object has no attribute 'get_descendant_count' | django-mptt

Question

Can someone help me to fix next problem. I use django-mptt application in my Django project. I want to make tree of related users. For this task I decided to create Profile model with next code.

from mptt.models import MPTTModel, TreeForeignKey

class Profile(MPTTModel):
    user = models.OneToOneField(
        User,
        on_delete=models.CASCADE,
    )
    referral = models.OneToOneField(
        Referral,
        null=True,
        on_delete=models.CASCADE,
    )
    parent = TreeForeignKey(
        User,
        on_delete=models.CASCADE,
        null=True, blank=True,
        related_name='children'
    )

class MPTTMeta:
    order_insertion_by = ['user']

Problem: In views.py I want to change parent field value of Profile object but has next error.

ERROR:

  File "C:\Users\PycharmProjects\Project\project_venv\lib\site-packages\mptt\models.py", line 209, in get_ordered_insertion_target
    if parent is None or parent.get_descendant_count() > 0:
AttributeError: 'User' object has no attribute 'get_descendant_count'

views.py:

print(self.created_user) # return correct value

profile = Profile.objects.get(id=5)
profile.parent = self.created_user
profile.save()

Answer 1

You can't define the parent as pointing to another class. That wouldn't make sense; the point of a tree is that you have a hierarchical set of items of the same type.

Your parent TreeForeignKey needs to point to "self", and you need to pass it an instance of Profile, not User.