Migrate form to modelform - django

Question

I wrote following form:
class VoteForm(forms.Form):
choice = forms.ModelChoiceField(queryset=None, widget=forms.RadioSelect)
def __init__(self, *args, **kwargs):
question = kwargs.pop('instance', None)
super().__init__(*args, **kwargs)
if question:
self.fields['choice'].queryset = question.choice_set
class VoteView(generic.UpdateView):
template_name = 'polls/vote.html'
model = Question
form_class = VoteForm
def get_queryset(self):
return Question.objects.filter(pub_date__lte=timezone.now()).exclude(choice__isnull=True)
def get_context_data(self, **kwargs):
context = super().get_context_data(**kwargs)
# Check duplicate vote cookie
cookie = self.request.COOKIES.get(cookie_name)
if has_voted(cookie, self.object.id):
context['voted'] = True
return context
def get_success_url(self):
return reverse('polls:results', args=(self.object.id,))
def form_valid(self, form):
redirect = super().form_valid(form)
# Set duplicate vote cookie.
cookie = self.request.COOKIES.get(cookie_name)
half_year = timedelta(weeks=26)
expires = datetime.utcnow() + half_year
if cookie and re.match(cookie_pattern, cookie):
redirect.set_cookie(cookie_name, "{}-{}".format(cookie, self.object.id), expires=expires)
else:
redirect.set_cookie(cookie_name, self.object.id, expires=expires)
return redirect
The problem is that the normal form does not represent a object does not have the save() method like ModelForm. But I can't figure out how to migrate the form. There is no choice or choice_set field:
class VoteForm(forms.ModelForm):
class Meta:
Model = Question
#throws exception
fields = ('choice',)
widgets = {
'choice': forms.RadioSelect()
}
EDIT:
Here are the models:
class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')
class Choice(models.Model):
question = models.ForeignKey(Question, on_delete=models.CASCADE)
choice_text = models.CharField(max_length=200)
votes = models.IntegerField(default=0)
How can the form from above be reproduced as a modelform?

Answer 1

Even if you have ModelForm you can define additional fields if you need them. In your case it will be choice field as in previous normal form.
Then in Meta you will exclude all the fields of the Question model which are not required.
After that in init you will provide choice set of provided instance to the choice field.
class VoteForm(forms.ModelForm):
choice = forms.ModelChoiceField(queryset=None, widget=forms.RadioSelect)
class Meta:
model = Question
exclude = ['question_text','pub_date']
def __init__(self, *args, **kwargs):
super(VoteForm, self).__init__(*args, **kwargs)
instance = getattr(self, 'instance', None)
if instance:
self.fields['choice'].queryset = instance.choice_set
The code is written online and not tested, but I think it should work.