Django save model with anonymous user

Question

I have a Django model:

class Project(models.Model):
    user = models.ForeignKey(User)
    zipcode = models.CharField(max_length=5)
    module = models.ForeignKey(Module)

In my views.py:

def my_view(request):  
    ...
    project = Project.objects.create(
                  user=request.user,
                  product=product_instance,
                  ...
              )
    project.save()

I want to be able to save user as an authenticated user OR an AnonymousUser (which I can update later). However, if I'm not logged in I get this error:

ValueError: Cannot assign "<django.utils.functional.SimpleLazyObject object at 0x1b498d0>": "Project.user" must be a "User" instance.

I guess that Django won't save the AnonymousUser because it is not a User as defined in the User model. Do I need to add the anonymous user to the User model, or am I missing something?

Any assistance much appreciated.

Thomas Orozco · Accepted Answer · 2012-12-20T01:45:29.137

18

The user field is a ForeignKey. That means it must reference some user.

By definition, the AnonymousUser is no user: in Django, there is no AnonymousUserA and AnonymousUserB. They're all the same: AnonymousUser.

Conclusion: you can't put an AnonymousUser in a User ForeignKey.

The solution to your issue is pretty straightforward though: when the User is anonymous, just leave the field blank. To do that, you'll need to allow it:

user = models.ForeignKey(User, blank = True, null = True)

edited Dec 20 '12 at 01:45

answered Dec 20 '12 at 01:18

Thomas Orozco

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1

Ok, great. So if I do `user=request.user` on an `AnonymousUser` then the field will be blank and no exception raised? – Darwin Tech Dec 20 '12 at 01:21
1

An Exception will be raised because you provided inappropriate data to the field. Just do `if request.user.is_authenticated(): project.user = request.user` – Thomas Orozco Dec 20 '12 at 01:23
Do I also have to add `null-True`, as the field cannot be `null`? – Darwin Tech Dec 20 '12 at 01:25
1

@DarwinTech `null = True` affects *how* a blank value is stored, not *whether it can be stored*. You can add it, but it won't change make a difference here. – Thomas Orozco Dec 20 '12 at 01:27
ok, with `blank = True` I generate the error: `IntegrityError: (1048, "Column 'user_id' cannot be null")`. I ran south against the change but it says nothing changed. – Darwin Tech Dec 20 '12 at 01:29
@DarwinTech Something *did* change. You might want to do the migration by hand then? – Thomas Orozco Dec 20 '12 at 01:32
But surely if I do not include `null = True` I will not be able to leave the field blank form the db point of view? – Darwin Tech Dec 20 '12 at 01:38
@DarwinTech Yep, you're right, sorry I got confused somewhere, do add it. South should pick up the migration once you do! : ) – Thomas Orozco Dec 20 '12 at 01:41
@DarwinTech Glad we finally got there! : ) – Thomas Orozco Dec 20 '12 at 01:53

score 0 · Answer 2 · answered Apr 07 '23 at 13:17

You might approach it like this where,

user = None
if request.user.is_authenticated:
    user = request.user

project = Project.objects.create(
              user=user,
              product=product_instance,
              ...
          )

And following this use the "user" in your methods. When it is anonymous user, it will be none.

Dont forget to define the user in your Project model as

user = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, blank=True, ...

Django save model with anonymous user

2 Answers2