python - Django, save ModelForm

Question

I have created a model Student which extends from the Django User and is a foreign key to another model while it has an integer field called year. What i'm trying to do is to save a form, which has 2 fields. The one is the course id and the another one is the the integer field year. When I'm clicking submit, i'm getting an error Cannot assign "u'2'": "Student.course" must be a "Course" instance.

models.py

class Student(models.Model):
    user = models.OneToOneField(User)
    course = models.ForeignKey(Course)
    year = models.IntegerField(validators=[MinValueValidator(1),
                                           MaxValueValidator(7)])

view.py

def step3(request):
    user = request.user
    if request.method == 'POST':
        form = SelectCourseYear(request.POST)
        if form.is_valid():
            form.save()
            return render_to_response("registration/complete.html", RequestContext(request))
    else:
        form = SelectCourseYear()
    return render(request, 'registration/step3.html',)

forms.py

class SelectCourseYear(forms.ModelForm):
    course = forms.CharField()
    year = forms.IntegerField(required=True)

    class Meta:
        model = Student
        fields = ['user', 'course', 'year']

Answer 1

You dont need to redefine fields in the ModelForm if you've already mentioned them in the fields attribute. So your form should look like this -

class SelectCourseYear(forms.ModelForm):
    class Meta:
        model = Student
        fields = ['course', 'year'] # removing user. we'll handle that in view

And we can handle the form with ease in the view -

def step3(request):
    user = request.user
    if request.method == 'POST':
        form = SelectCourseYear(request.POST)
        if form.is_valid():
            student = form.save(commit=False)
            # commit=False tells Django that "Don't send this to database yet.
            # I have more things I want to do with it."

            student.user = request.user # Set the user object here
            student.save() # Now you can send it to DB

            return render_to_response("registration/complete.html", RequestContext(request))
    else:
        form = SelectCourseYear()
    return render(request, 'registration/step3.html',)