How do I extend the Django Group model?

Question

Is there a way to extend the built-in Django Group object to add additional attributes similar to the way you can extend a user object? With a user object, you can do the following:

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

and add the following to the settings.py file

AUTH_PROFILE_MODULE = 'app.UserProfile' 

which gets you:

profile = User.objects.get(id=1).get_profile() 

Is there any equivalent to this approach for extending a group? If not, is there an alternative approach I can take?

Answer 1

If you simply subclass the Group object then by default it will create a new database table and the admin site won't pick up any new fields.

You need to inject new fields into the existing Group:

if not hasattr(Group, 'parent'):     field = models.ForeignKey(Group, blank=True, null=True, related_name='children')     field.contribute_to_class(Group, 'parent') 

To add methods to the Group, subclass but tag the model as proxy:

class MyGroup(Group):      class Meta:         proxy = True      def myFunction(self):         return True 

Answer 2

You can create a model that subclasses Group, add your own fields, and use a Model Manager to return any custom querysets you need. Here's a truncated example showing how I extended Group to represent Families associated with a school:

from django.contrib.auth.models import Group, User  class FamilyManager(models.Manager):     """     Lets us do querysets limited to families that have      currently enrolled students, e.g.:         Family.has_students.all()      """     def get_query_set(self):         return super(FamilyManager, self).get_query_set().filter(student__enrolled=True).distinct()   class Family(Group):     notes = models.TextField(blank=True)      # Two managers for this model - the first is default      # (so all families appear in the admin).     # The second is only invoked when we call      # Family.has_students.all()       objects = models.Manager()     has_students = FamilyManager()      class Meta:         verbose_name_plural = "Families"         ordering = ['name']      def __unicode__(self):         return self.name