django – update model with FormView and ModelForm

For any further visitors of this thread, yes, you can make a FormView that acts like both a CreateView and an UpdateView. This, despite some opinions of other users, can make a lot of sense if you want to have a single form/URL/page for a web form to save some user data which can be optional but needs to be saved once and only once. You don’t want to have 2 URLs/views for this, but just only one page/URL which shows a form, filled with previous data to be updated if a model was already saved by the user.

Think in a kind of “contact” model like this one:

from django.conf import settings
from django.db import models


class Contact(models.Model):
    """
    Contact details for a customer user.
    """
    user = models.OneToOneField(settings.AUTH_USER_MODEL)
    street = models.CharField(max_length=100, blank=True)
    number = models.CharField(max_length=5, blank=True)
    postal_code = models.CharField(max_length=7, blank=True)
    city = models.CharField(max_length=50, blank=True)
    phone = models.CharField(max_length=15)
    alternative_email = models.CharField(max_length=254)

So, you write a ModelForm for it, like this:

from django import forms

from .models import Contact


class ContactForm(forms.ModelForm):
    class Meta:
        model = Contact
        exclude = ('user',)  # We'll set the user later.

And your FormView with both “create” and “update” capabilities will look like this:

from django.core.urlresolvers import reverse
from django.views.generic.edit import FormView

from .forms import ContactForm
from .models import Contact


class ContactView(FormView):
    template_name="contact.html"
    form_class = ContactForm
    success_url = reverse('MY_URL_TO_REDIRECT')

    def get_form(self, form_class):
        """
        Check if the user already saved contact details. If so, then show
        the form populated with those details, to let user change them.
        """
        try:
            contact = Contact.objects.get(user=self.request.user)
            return form_class(instance=contact, **self.get_form_kwargs())
        except Contact.DoesNotExist:
            return form_class(**self.get_form_kwargs())

    def form_valid(self, form):
        form.instance.user = self.request.user
        form.save()
        return super(ContactView, self).form_valid(form)

You don’t even need to use a pk in the URL of this example, because the object is retrieved from the DB via the user one-to-one field. If you have a case similar than this, in which the model to be created/updated has a unique relationship with the user, it is very easy.

Hope this helps somebody…

Cheers.