ModelForm and Model validation playing together - django

Question

I have the following Model :
class Advertisement(models.Model):
slug = models.UUIDField(default=uuid4, blank=True, editable=False)
advertiser = models.ForeignKey(Advertiser)
position = models.SmallIntegerField(choices=POSITION_CHOICES)
share_type = models.CharField(max_length=80)
country = CountryField(countries=MyCountries, default='DE')
postal_code = models.CharField(max_length=8, null=True, blank=True)
date_from = models.DateField()
date_to = models.DateField()
Based on Advertiser, position, type country and postal code this stores adverisements with range date_from and date_to.
advertiser, position, share_type, country and postal_code
are coming from the request and are fetched in
class CreateAdvertisment(LoginRequiredMixin, CreateView):
# Some usefull stuff
def dispatch(self, request, *args, **kwargs):
self.advertiser = Advertiser.objects.get(user=self.request.user)
self.share_type = self.kwargs.get('share_type', None)
self.country = self.kwargs.get('country', None)
self.postal_code = self.kwargs.get('postal_code', None)
self.position = int(self.kwargs.get('position', None))
self.position_verbose = verbose_position(self.position)
ret = super(CreateAdvertisment, self).dispatch(request, *args, **kwargs)
return ret
Without any validation for checking date_from, date_to. I can simply do
def form_valid(self, form):
form.instance.advertiser = self.advertiser
form.instance.share_type = self.share_type
form.instance.country = self.country
form.instance.postal_code = self.postal_code
form.instance.position = self.position
ret = super(CreateAdvertisment, self).form_valid(form)
return ret
and I am done. Unfortunatly I cannot do this as I do have to check for valid time Frames for the Advertisment to avoid Double Bookings of the same time. I do this in the model with the following :
def clean(self):
ret = super(Advertisement, self).clean()
print ("country [%s] position [%s] share_type [%s] postal_code [%s]" % (self.country,
self.position, self.share_type, self.postal_code))
if self.between_conflict():
raise ValidationError("Blocks between timeframe")
elif self.end_conflict():
raise ValidationError("End occupied")
elif self.during_conflict():
raise ValidationError("Time Frame complete occupied")
elif self.start_conflict():
raise ValidationError("Start Occupied")
return ret
def start_conflict(self):
start_conflict = Advertisement.objects.filter(country=self.country,
position=self.position,
share_type=self.share_type,
postal_code=self.postal_code).filter(
date_from__range=(self.date_from, self.date_to))
return start_conflict
This works well and I filter out any Conflict for the given period. Problem is that I do not have the instance variables as they are set in view.form_valid() and model.clean() is called by the form validation process.
I do have an chicken egg problem here. I am thinking about setting the requests parameters to the form kwargs in
def get_form_kwargs(self, **kwargs):
kwargs = super(CreateAdvertisment, self).get_form_kwargs()
kwargs['advertiser'] = self.advertiser
kwargs['position'] = self.position
....
and then putting them into the form instance in form.init()
def __init__(self, *args, **kwargs):
advertiser = kwargs.pop('advertiser')
position = kwargs.pop('position')
# .. and so on
super(AdvertismentCreateForm, self).__init__(*args, **kwargs)
For some reasons I do not think this is very pythonic. Does anybody have a better idea? I will post my solution.

Answer 1

I think that overriding get_form_kwargs is ok. If all the kwargs are instance attributes, then I would update the instance in the get_form_kwargs method. Then you shouldn't have to override the form's __init__, or update the instance's attributes in the form_valid method.
def get_form_kwargs(self, **kwargs):
kwargs = super(CreateAdvertisment, self).get_form_kwargs()
if kwargs['instance'] is None:
kwargs['instance'] = Advertisement()
kwargs['instance'].advertiser = self.advertiser
...
return kwargs
In the model's clean method, you can now access self.advertiser.

Answer 2

alasdairs proposal works fine I have the following now :
def get_form_kwargs(self, **kwargs):
kwargs = super(CreateAdvertisment, self).get_form_kwargs()
if kwargs['instance'] is None:
kwargs['instance'] = Advertisement()
kwargs['instance'].advertiser = self.advertiser
kwargs['instance'].share_type = self.share_type
kwargs['instance'].country = self.country
kwargs['instance'].postal_code = self.postal_code
kwargs['instance'].position = self.position
return kwargs
def form_valid(self, form):
ret = super(CreateAdvertisment, self).form_valid(form)
return ret
Of course there is no need to override form_valid anymore. I have just included here in order to display that we do not set the instance fields anymore as this is done in get_form_kwargs() already