'RelatedManager' object has no attribute 'save'

Question

This is the models.py code

class Profile(models.Model):
    user = models.ForeignKey(User, unique=True, on_delete=models.CASCADE, related_name='profile')



@receiver(post_save, sender=User)
def update_user_profile(sender, instance, created, **kwargs):
    if created:
        Profile.objects.create(user=instance)
    instance.profile.save()


@receiver(post_save, sender=User)
def save_user_profile(sender, instance, **kwargs):
    # Profile.objects.save()
    instance.profile.save()

and This the views.py code:

def signup(request):
    ....

    if request.method == "POST":
        user_form = UserRegistrationForm(request.POST)

        if user_form.is_valid():
            user = user_form.save(commit=False)
            user.save(using='default')
            login(request, user)
            return HttpResponse("User Loged In")

Then after fill the registration form and click the submit button, Django get me the following Error:

Answer 1

You defined a ForeignKey from a Profile to a User , but that means every Profile is attached to a User , it is however perfectly possible that multiple Profile s are attached to the same User .

Hence if you use a_user.profile , it will not return a single Profile , but a RelatedManager : a manager that manages the collection (that can contain zero, one or multiple elements) of Profile .

I think however that you actually want to associated Profile s with distinct User s, in which case you better use a OneToOneField :

class Profile(models.Model):
    user = models.(User, unique=True, on_delete=models.CASCADE)

If you then query someuser.profile you will either get a Profile instance, or it will raise a Profile.DoesNotExists error in case no profile is associated with that user.

By default the related_name of a OneToOneField is the name of the class in lowercase, so you no longer need to specify this.

Note however that in your code instance.profile.save() is not necessary, since the Profile , is basically already saved by creating it:

@receiver(post_save, sender=User)
def update_user_profile(sender, instance, created, **kwargs):
    if created:
        Profile.objects.create(user=instance)
    # unnecessary
    # instance.profile.save()