Django: "Model2.user" must be a "User" instance

Question

I have the below models:

class Model1(models.Model):
    Field1 = models.CharField(max_length=200)

class Model2(models.Model)
    Field2 = models.ForeignKey(Model1, on_delete=models.CASCADE)
    Field3 = models.ForeignKey(User, on_delete=models.CASCADE)
    Email = models.EmailField(null=TRUE)

And here's my forms.py:

class Model1Form(ModelForm):
    class Meta:
        model = Model1
        fields = ['Field1']

class Model2Form(ModelForm):
    class Meta:
        model = Model2
        fields = ['email']


Model2Field2Formset = inlineformset_factory(Model1, Model2, form=Model2Form, extra=1)
Model2Field3Formset = inlineformset_factory(User, Model2, form=Model2Form, extra=1)

And here's my views.py:

class NewEntry(CreateView):
    model = Model1
    fields = ['Field1']
    success_url = reverse_lazy('voting:index')

    def get_context_data(self, **kwargs):
        data = super().get_context_data(**kwargs)
        if self.request.POST:
            data['model2_field2'] = Model2Field2Formset(self.request.POST)
            data['model2_field3'] = Model2Field3Formset(self.request.POST)
        else:
            data['model2_field2'] = Model2Field2Formset()
            data['model2_field3'] = Model2Field3Formset()
        return data

    def form_valid(self, form):
        context = self.get_context_data()
        model2_field2 = context['model2_field2']
        model2_field3 = context['model2_field3']
        with transaction.atomic():
            self.object = form.save()
            if model2_field2.is_valid() and model2_field3.is_valid():
                model2_field2.instance = self.object
                model2_field2.save()
                model2_field3.instance = self.object
                model2_field3.save()

        return super().form_valid(form)

I'm trying to create an entry for Model1, Field1. Then, using inlineformset_factory, create multiple email entries in Model2 that each one is associated with the same Field1_id entry and the respective user_id of each email in the form.

But I'm getting a "Model2.user" must be a "User" instance. error on the model2_field3.save() line of code. If I comment out that line there are no errors and the entries are saved as expected except the Field3 column which remains NULL.

This is the traceback of the error:

Environment:


Request Method: POST
Request URL: http://127.0.0.1:8000/polls/newpoll/

Django Version: 2.0.5
Python Version: 3.5.2
Installed Applications:
['secvot',
 'accounts.apps.AccountsConfig',
 'voting.apps.VotingConfig',
 'django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware']



Traceback:

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/core/handlers/exception.py" in inner
  35.             response = get_response(request)

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/core/handlers/base.py" in _get_response
  128.                 response = self.process_exception_by_middleware(e, request)

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/core/handlers/base.py" in _get_response
  126.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/views/generic/base.py" in view
  69.             return self.dispatch(request, *args, **kwargs)

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/views/generic/base.py" in dispatch
  89.         return handler(request, *args, **kwargs)

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/views/generic/edit.py" in post
  172.         return super().post(request, *args, **kwargs)

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/views/generic/edit.py" in post
  142.             return self.form_valid(form)

File "/home/kostis/PycharmProjects/secvot/voting/views.py" in form_valid
  110.                 eligible_voters_user.save()

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/forms/models.py" in save
  670.         return self.save_existing_objects(commit) + self.save_new_objects(commit)

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/forms/models.py" in save_new_objects
  804.             self.new_objects.append(self.save_new(form, commit=commit))

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/forms/models.py" in save_new
  943.         setattr(form.instance, self.fk.name, self.instance)

File "/home/kostis/.virtualenvs/secvote/lib/python3.5/site-packages/django/db/models/fields/related_descriptors.py" in __set__
  197.                     self.field.remote_field.model._meta.object_name,

Exception Type: ValueError at /polls/newpoll/
Exception Value: Cannot assign "<Poll: asdefrgrs>": "EligibleVoters.user" must be a "User" instance.

Just a sidenote, the EligibleVoters model is the respective Model2 in my question. I renamed and removed a few fields to keep my question simpler.

This is what I'm trying to achieve:

Basically a model with two foreign keys (two parent models). Create a single Field1 entry and then using inlineformset_factory create multiple email entries in Model2 associated with that single Field1 entry and the respective user_id of each email.

Answer 1

In your form_valid() method you are assigning the same self.object to model2_field2 and model2_field3, which can not possibly be correct since they are foreign keys to different models. Most likely you are trying to assign an instance of Model1 to model2_field3 where you should be assigning an instance of User to that field.