I'm trying to figure out the best way to set up the following django model (genericised for security reasons).

ThingA:User(M2M through "UserRelation")ThingB:User(M2M through "UserRelation")ThingC:User(M2M through "UserRelation")User:Login_nameUserRelation:User (foreginkey)Thing (foreignkey) #is this generic to any of the above "things"Privilege

I understand using "through" between two distinct models, but I'm not sure how to apply this to multiple models. Would I define a foreignkey for each of the "Thing" models in my UserRelation Model?

It looks like you are trying to setup a generic many-to-many relationship. There is a dedicated django app that you can be use for this purpose: django-gm2m

Here is how to use it in your generic case:

from django.db import models
from django.contrib.contenttypes.fields import GenericForeignKeyfrom gm2m import GM2MFieldclass ThingA(models.Model):passclass ThingB(models.Model):passclass ThingC(models.Model):passclass User(models.Model):login_name = models.CharField(max_length=255)things = GM2MField(through='UserRelation')class UserRelation(models.Model):user = models.ForeignKey(User)thing = GenericForeignKey(ct_field='thing_ct', fk_field='thing_fk')thing_ct = models.ForeignKey(ContentType)thing_fk = models.CharField(max_length=255)privilege = models.CharField(max_length=1)

You can now access all the things for a given user and all the User instances for a given 'thing', as well as the privilege attribute for each UserRelation instance.

This will additionally provide you with a handful of benefits (reverse relations, prefetching, etc.) you may need. A GM2MField basically behaves exactly like a django ManyToManyField.

Disclaimer: I am the author of django-gm2m