Django submit optional forms - django

Question

I need to create registration form for an event. Each person that register can bring guests. I want to register everything in one page. To do that I use a view with 1 RegistrationForm and X GuestForms. In my models, I have a Registration and Guest class I used to create the two forms with ModelForm.
The problem is that a GuestForm is not required to be filled (you don't have to bring guests).
def register_form(request):
error = False
if request.method == 'POST':
register = RegistrationForm(request.POST, instance=Registration() )
guests = [GuestForm(request.POST, prefix=str(x), instance=Guest()) for x in range(MAXGUESTS)]
if register.is_valid():
print("register is valid")
for guest in guests:
if guest.is_valid():
print("guest is valid")
else:
print("guest is not valid") # always when empty form
error = True
else:
print("register is not valid")
error = True
if not error:
... # save the form in the database
register = RegistrationForm(instance=Registration())
guests = [GuestForm(prefix=str(x), instance=Guest()) for x in range(MAXGUESTS)]
return render_to_response('register.html',{
'form': register,
'max_guests': MAXGUESTS,
'guests': guests,
'error': error,
})
So I need to set a form as optional and be able to differentiate when the whole form is empty and when there is an error. Any idea how ?
Thank you
Solution
def register_form(request):
GuestFormSet = modelformset_factory(Guest, exclude=('register',))
error = False
if request.method == 'POST':
register = RegistrationForm(request.POST, instance=Registration() )
guests = GuestFormSet(request.POST)
if register.is_valid():
print("register is valid")
for guest in guests:
if guest.is_valid():
print("guest is valid") # even if some forms are empty
else:
print("guest is not valid")
error = True
else:
print("register is not valid")
error = True
if not error:
...
# save the form in the database
return something
else:
register = RegistrationForm(instance=Registration())
guests = GuestFormSet(queryset=Guest.objects.none())
return render_to_response('register.html',{
'form': register,
'max_guests': MAXGUESTS,
'guests': guests,
'error': error,
})

Answer 1

You can use a model formset for your guest forms. It can distinguish between empty and invalid forms.
https://docs.djangoproject.com/en/dev/topics/forms/modelforms/#model-formsets

Answer 2

I guess you will need some way to determine if a submitted guest form was actually filled in. When an empty form was submitted, ignore it:
forms_to_save =[]
for form in guest_forms:
if guest_form.is_valid()
forms_to_save.append( form )
else:
if form.contains_data(): # you'll have to implement this
error = True
if not error:
for form in forms_to_save():
form.save()

Answer 3

I have a similar problem in a wedding RSVP application that I'm building. In my case, each Guest has an 'attending' checkbox, and if it is not checked (i.e. the guest isn't attending) then I don't want any errors to be reported to the user.
My Guest model (slimmed down for brevity):
class Guest(models.Model):
email = models.EmailField(max_length=50, unique=True)
first_name = models.CharField(max_length=50)
last_name = models.CharField(max_length=50)
attending = models.BooleanField(default=False)
I have a ModelForm class called RsvpForm that creates a form based on the Guest model. It looks like this:
class RsvpForm(ModelForm):
class Meta:
model = Guest
fields = ('attending', 'email', 'first_name', 'last_name')
def clean(self):
cleaned_data = self.cleaned_data
attending = cleaned_data.get('attending')
if not attending:
#clear the error collection
self._errors['email'] = {}
return cleaned_data
The solution to this problem lies in the clean() method that I've overriden in my RsvpForm class. In it, I check whether or not the guest is attending. If they aren't, then I clear the error messages for each of the other fields.
Originally, I had cleared the errors for the entire form like this:
if not attending:
#clear the error collection
self._errors['email'] = ''
self._errors['first_name'] = ''
self._errors['last_name'] = ''
But for some reason, modifying the values of any of these keys caused the form to fail validation, which in turn prevented Guest data from being saved if they had indicated that they were not attending. A small bug that most would never find, but annoying nonetheless.
At some point along the line, I had also tried to clear the errors collection by calling .clear() on the self._errors dictionary:
if not attending:
#clear the error collection
self._errors.clear()
But for some reason, the errors were still shown, even though I could verify that the dictionary was empty.
The end result is that form validation errors are only shown to my user if the 'attending' checkbox is selected, which is ideal because Guests might want to update their own contact information prior to deciding on who they will bring as a plus one.

Answer 4

There is a simpler solution than Alasdair's: using the empty_permitted keyword argument.
>>> f = MyForm(data={}, empty_permitted=True)
>>> f.is_valid()
True