Question

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Validating a form with overloaded init

I’ve spent the entire afternoon trying to figure out what I’m doing wrong here, and I know it’s going to be something face-palmingly stupid. When the user fills out a form, the location selection box depends on the country of the user and lists different cities accordingly.

Model & Modelform

class Cars(models.Model):
    owner = models.ForeignKey(User)
    name = models.CharField(max_length=25)
    location = models.PositiveIntegerField(default=1)
    created = models.DateTimeField(default=utc_time)

class CarsForm(ModelForm):
    def __init__(self, country, *args, **kwargs):
        super(CarsForm, self).__init__(*args, **kwargs)
        self.fields['location'] = forms.ModelChoiceField(queryset=Cities.objects.filter(country=country))

    class Meta:
        model = Cars
        exclude = ('owner', 'created',)

View

def new_car(request):
    if request.method == u'POST' and request.is_ajax():
        form = CarsForm(request.POST)
        if form.is_valid():
                      etc...

Following advice from stackoverflow, I edited the modelform init to allow the country variable to be passed. The form creation and html displays fine and everything works great, only now the form won’t validate.

UPDATE:
Ok, it looks like I (meaning ‘YOU’) got it working. Several things were ugly, and once fixed it works ok:

• the location field type was changed to foreignkey, correcting the
  data mismatch issue
• the init was revised to accept country as a kwarg
• the form validation now passes the variable as a kwarg
  CarsForm(request.POST, country=country)

SUCCESS! In under an hour. Thanks so much everyone!!

Answer 1

Either this is the solution, or your copy-and-pasting has problems ;)

You’ve correctly defined the over-ridden __init__ method, but you’re not actually passing a country parameter; doing so would look like this:

form = CarsForm(country, request.POST)

This means that request.POST always gets stored in country and never passed on to the parent class’s __init__ method.

If the form gets no data, is_valid() will always return False.

A side-note: where does SkillForm come from? Should be CarsForm.