Django: Save and restore a form's state using a cookie

Question

I want to make a form that once submitted, on each next rendering of the form for the same user, the form will be already filled out with the data from the last time the user su

Answer 1

This already sounds like a good plan. But if there is no pressure on using cookies, I would resort to using the session instead. That way you won't hit a size limit on cookies, and transmitting cookies with higher size can slow down your response time.

form = MyForm(initial=request.session.get('form_data'))
...
if form.is_valid():
    request.session['form_data'] = form.cleaned_data

Answer 2

As an extension to this, here is a way I have found to use sessions to save the form data with a class-based view:

from django.views.generic.edit import FormView

class MyFormView(FormView):
    template_name = 'myform.html'
    form_class = MyForm
    success_url = '/success/'

    def get_form_kwargs(self):
        """
        The FormMixin uses this to populate the data from the POST request.
        Here, first try to populate it from the session data, if any;
        if there is POST data, it should override the session data.
        """
        kwargs = {'data': self.request.session.get('form_data', None)}
        kwargs.update(super(MyFormView, self).get_form_kwargs())
        return kwargs

    def form_valid(self, form):
        ...
        # save the form data to the session so it comes up as default next time
        self.request.session['form_data'] = form.cleaned_data
        ...