django : models with reverse foreignkeys?

Question

I've got a chicken and egg problem here. Firstly I've got a userprofile class which builds upon the default user model of django.

class UserProfile(models.Model):
    def __unicode__(self):
        return self.user.username
    user = models.OneToOneField(User, unique=True)
    exam = models.ForeignKey('questions.Exam', null=True)

Next, I've got an Exam class

class Exam(models.Model):
    def __unicode__(self):
        return self.id
    user = models.ForeignKey(UserProfile)

The UserProfile and Exam models are in different apps. However, they both have foreignkey to each other. I know its bad design, but its my peculiar requirement in my case. However UserProfile foreignkey to Exam can be Null. But whenever I try to create Exam in Admin, I get error saying "UserProfile" is a required field. And when I try to create User, the reverse happens. Is there a way to break this deadlock? Or should I redesign my app?

Answer 1

should I redesign my app?

Almost certainly. However, this actual problem is caused by the fact that you have null=True, which correctly sets up the database to allow nulls on the foreign key field, but you have not added blank=True, which is what Django uses to validate correct entries. Add that, and this part at least should work.