Django，ManyToManyField（model），同时定义模型

Question

I'm new to Django and I've encountered some problem: I'm trying to prepare website where users can attach themselves to custom model "UserGroup" (not these from User.group) so they'll become it's members as ManyToManyField relation. But I would like also to add information to these groups whether they're linked to other groups. How can do such thing? I've tried to do this like here, in UserGroup definition:

related_groups = models.ManyToManyField('UserGroup', blank=True)

But apparently I can't do that this way, I'm getting some problems during migration:

django.core.exceptions.FieldDoesNotExist: UserGroup_related_groups has no field named 'from_usergroup '

I suppose it might be because of faulty way of thinking. Thanks for help in advance! :)

Answer 1

1. You are using wrong name of class for user groups. The correct name is Group
2. You should use OneToOne Field.

So you should write something like:

related_groups = models.OneToOneField('Group', blank=True)

And don't forget to import Group model before!

from django.contrib.auth.models import Group

PS There are 2 ways to do this: 1) To make your own class (ie ExtGroup) and make OneToOneField to original Group Class. You probably were trying to go this way. 2) Use your own user class and group class.

Here is really nice documentation about each way: https://docs.djangoproject.com/en/1.10/topics/auth/customizing/#extending-the-existing-user-model

And here is answer for the same question: Customize Django Group Model

Hope it helps ;)

Answer 2

Use "self" to indicate that you are linking to the same class.

related_groups = models.ManyToManyField("self", blank=True)

As suggested in this SO post Django Many-to-Many (m2m) Relation to same model