ModelFormMixin have extra logic in get_form_kwargs that crash view

[lagovas.lagovas@…]

When view inherit FormView and ModelFormMixin, have correct form_class and model fields, view will crash with AttributeError at /
'AddNoteView' object has no attribute 'object'

in this code:

class ModelFormMixin:
    ....
    def get_form_kwargs(self):
        """
        Returns the keyword arguments for instantiating the form.
        """
        kwargs = super(ModelFormMixin, self).get_form_kwargs()
        kwargs.update({'instance': self.object})
        return kwargs

It's due to accessing to self.object before form.save(). Even in get request, when object can't be exist.

To check this you need inherit from FormView and ModelFormMixin:

class AddNoteView(FormView, ModelFormMixin):

template_name = 'notes.html'
form_class = NoteForm
success_url = reverse_lazy('index')
model = Note

[lagovas.lagovas@…]

screenshot of traceback

[Baptiste Mispelon]

Hi,

If you're combining ModelFormMixin and FormView, I think you'd be better off using a CreateView.
And if you find yourself writing complex code, it might be a sign that it's time to drop Django's generic mixins and write your own view from scratch (inheriting from View).

Having said that, the implementation of ModelFormMixin.get_form_class has some code that makes sure self.object exists so for consistency's sake, I'll mark this as accepted.

The change is pretty straightforward so I'll also mark the ticket as easy picking.

Thanks.

[Ryan Kaskel]

Fixed here: ​https://github.com/django/django/pull/2248

[Tim Graham <timograham@…>]

In 75a96f06e916dda9124da9ddf765f3b8d5530914:

Fixed #21967: Added check for object in ModelFormMixin.get_form_kwargs.

Thanks lagovas.lagovas at gmail.com for the report.