Save new foreign key with django form

Question

I have two models:

class Studio(models.Model):
    name = models.CharField(\"Studio\", max_length=30, unique=True)

class Film(models.Model):
    studio = mo         


        

Answer 1

I stumbled across this question and I think I got a better answer for future seekers.

Django comes with something called Inline Formsets which helps you manage relationships in a form.

You just have to create your model like you did with their respective ForeignKeys. Then in the Forms.py import this

from django.forms.models import inlineformset_factory

Then:

YOUR_FORMSET = inlineformset_factory(Model1,Model2)

Back on yout views.py you should import both your Form and your new created YOUR_FORMSET.

After doing this, your method should use the inlineformset like this:

def add_question(request):

    if request.method == 'POST':


      form =AddQuestionForm(request.POST, request.FILES)
      if form.is_valid():
          new_question = form.save(commit=False)

          question_formset = QuestionFormset(request.POST, instance=new_question)
          if question_formset.is_valid():
              form.save()
              question_formset.save()
              return HttpResponseRedirect(reverse('polls:detail',args=(new_question.pk,)))
      else:
          print(form.errors)
    else:
        form = AddQuestionForm()
        question_formset = QuestionFormset(instance=Question())
    return render(request, 'polls/add.html', {'form':form, 'question_formset':question_formset,})

I'm using my own example but the idea is explained.

If you want to read a more specific explication read this awesome blog post that I found.

Answer 2

Really, your only problem is that you've used a standard Form instead of a ModelForm. Form doesn't have a save method because it's not inherently tied to anything (i.e. it doesn't know what to save or where to save to).

However, if you use a ModelForm you need to take care of all logic involved in creating a new studio in the form. This is actually better, though, because then you can just use the form and not worry about anything else: the form holds all the logic needed to properly save itself.

class FilmForm(forms.ModelForm):
    class Meta:
        model = Film

    # only need to define `new_studio`, other fields come automatically from model
    new_studio = forms.CharField(max_length=30, required=False, label = "New Studio Name")

    def __init__(self, *args, **kwargs):
        super(FilmForm, self).__init__(*args, **kwargs)
        # make `studio` not required, we'll check for one of `studio` or `new_studio` in the `clean` method
        self.fields['studio'].required = False

    def clean(self):
        studio = self.cleaned_data.get('studio')
        new_studio = self.cleaned_data.get('new_studio')
        if not studio and not new_studio:
            # neither was specified so raise an error to user
            raise forms.ValidationError('Must specify either Studio or New Studio!')
        elif not studio:
            # get/create `Studio` from `new_studio` and use it for `studio` field
            studio, created = Studio.objects.get_or_create(name=new_studio)
            self.cleaned_data['studio'] = studio

        return super(FilmForm, self).clean()

Then, in your view, all you need is:

if form.is_valid():
    form.save()