Django Formsets: How to apply different validation to each form in formset?

Question

I'm using Django 1.4 formsets and I'd like to perform different validation for the first form in the formset.

I have a LocationForm where I display 4 text fields allowing the user to enter up to 4 locations:

class LocationForm(forms.Form):
    user_entered_address = forms.CharField(required=False, max_length=255)
    full_address = forms.CharField(max_length=255, required=False, widget=forms.HiddenInput())
    city = forms.CharField(max_length=255, required=False, widget=forms.HiddenInput())
    state = forms.CharField(max_length=255, required=False, widget=forms.HiddenInput())
    country = forms.CharField(max_length=255, required=False, widget=forms.HiddenInput())
    latitude = forms.CharField(required=False, widget=forms.HiddenInput())
    longitude = forms.CharField(required=False, widget=forms.HiddenInput())

LocationFormSet = formset_factory(LocationForm, extra=4, max_num=4)

This works great to display the input fields, but I would like the first LocationForm in the formset to be required and the rest of the forms to be optional (meaning the user must enter at least 1 location in the first form, but the rest are optional).

If I modify the form, removing required=False:

    user_entered_address = forms.CharField(max_length=255)

Then user_entered_address is required for all forms. I have a feeling I need to write a custom clean() method, but I'm stuck how to find the first form, figure out if user_entered_address is blank and if so, raise a ValidationError:

class BaseLocationFormSet(BaseFormSet):
    def clean(self):
        # How to do I find the first form and ensure user_entered_address isn't blank?

LocationFormSet = formset_factory(LocationForm, extra=4, max_num=4, formset=BaseLocationFormSet)

Or is this the wrong approach and there is a better way to do this? Thanks!

Answer 1

You can access the forms like:

form = self.forms[0]

So in your clean just check the first form and ignore the others.

form = self.forms[0]
title = form.cleaned_data['title']
if title is None:
    raise forms.ValidationError("Missing title")