Django: Set initial value for ForiegnKey in a CreateView

Question

I'm trying to create a view of type CreateView. This view will take the form_class = CourseForm that I created and excluded some fields in it. The instructor field is a foriegnKey and I don't want the user to be able to control it in the form. It's a field that depends on the signed in user.

# forms.py
class CourseForm(forms.ModelForm):
    class Meta:
        model = Course
        exclude = ['instructor', 'members', 'slug']
    # ...

my view is as follows. I thought that by including the instructor value in initial would pass the profile instance when I submit

# views.py

@method_decorator(login_required, name='dispatch')
class CourseCreateView(CreateView):
    model = Course
    template_name = 'course_form.html'
    success_url = reverse_lazy('course-create-complete')

    form_class = CourseForm

    def get_initial(self):
        initial = super(CourseCreateView, self).get_initial()
        initial = initial.copy()
        profile = get_object_or_404(Profile, user__username=self.request.user)
        initial['instructor'] = profile
        return initial


# models.py

class Course(models.Model):
    instructor = models.ForeignKey(Profile, related_name="Instructor")
    # ... other fields

but the probelm is that whenever I submit the form I get the following error:

NOT NULL constraint failed: myapp_course.instructor_id

score 1 · Accepted Answer · answered Jun 07 '16 at 18:48

If you want to set the initial value of instructor field, you shouldn't exclude it from the form. You could instead make the field hidden.

Or you could include that in the exclude list, but then you shouldn't override get_initial method, but do the assignment manually:

class CourseCreateView(CreateView):
    def form_valid(self, form):
        self.object = form.save(commit=False)
        # create instructor based on self.request.user
        self.object.instructor = instructor
        self.object.save()
    return HttpResponseRedirect(self.get_success_url())

Check django doc about what does save(commit=False) do.

Also check django doc about form_valid function and how forms are handled in class based views.

In this case, I think excluding is the better solution; otherwise you need to validate the user input. Your second solution is therefore much preferred. — Matthew Schinckel, Nov 22 '17 at 03:46
...however, I think you can rewrite it to set the instructor _before_ saving (and then just return `super(...)`). — Matthew Schinckel, Nov 22 '17 at 03:46

Django: Set initial value for ForiegnKey in a CreateView

1 Answers1