Django CBV Forms prepopulated foreign key dataset - django

Question

I'm trying to use CBVs as much as possible and want to pre-populate data in a ModelForm based on a generic.CreateView with some data passed in via URL.
I might be over thinking or confusing myself. All code abridged for legibility
We have an inventory system with PartNumbers (abstractions), Carriers (actual instances of PartNumbers with location, serial and quantity numbers) and Movements for recording when items are extracted from the inventory, how much is taken and what Carrier it came from.
I would like to have the "extract inventory" link on the PartNumber detail page, and then have the available carriers ( pn.carrier_set.all() ) auto filled into the FK drop down on the MovementForm.
models.py
class PartNumber(models.Model):
name = models.CharField("Description", max_length=100)
supplier_part_number = models.CharField(max_length=30, unique=True)
slug = models.SlugField(max_length=40, unique=True)
class Carrier(models.Model):
part_numbers = models.ForeignKey(PartNumber)
slug = models.SlugField(max_length=10, unique=True, blank=True, editable=False)
location = models.ForeignKey(Location)
serial_number = models.CharField(max_length=45, unique=True, null=True, blank=True)
qty_at_new = models.IntegerField()
qty_current = models.IntegerField()
class Movement(models.Model):
carrier = models.ForeignKey(Carrier)
date = models.DateField(default=timezone.now())
qty = models.IntegerField()
I have been playing around with get_initial() and get_form_kwargs() without success:
In urls.py I collect the PartNumber via url as pn_slug
url(r'^partnumber/(?P<pn_slug>[-\w]+)/extract/$', views.MovementCreate.as_view(), name='pn_extract'),
forms.py is generic
class MovementForm(forms.ModelForm):
class Meta:
model = Movement
views.py
class MovementCreate(generic.CreateView):
form_class = MovementForm
model = Movement
def get_form_kwargs(self):
kwargs = super(MovementCreate, self).get_form_kwargs()
kwargs['pn_slug'] = self.request.POST.get("pn_slug")
return kwargs
# here we get the appropriate part and carrier and.
# return it in the form
def get_initial(self):
initial = super(MovementCreate, self).get_initial()
# this didn't work, hence using get_form_kwargs
#pn = PartNumber.objects.get(slug=self.request.POST.get("pn_slug"))
pn = PartNumber.objects.get(slug=self[pn_slug])
carriers = pn.carrier_set.all()
initial['carrier'] = carriers
return initial
As it stands, I'm getting "global name 'pn_slug' is not defined" errors - but I doubt that error accurately reflects what I have done wrong.
I have been using these posts as rough guidelines:
How to subclass django's generic CreateView with initial data?
How do I use CreateView with a ModelForm

Answer 1

If I understand you correctly from our comments, all you need is just to change the queryset of the MovementForm's carrier field to set the available options. In that case, I would use get_initial nor get_form_kwargs at all. Instead, I would do it in get_form:
def get_form(self, *args, **kwargs):
form = super(MovementCreate, self).get_form(*args, **kwargs)
pn = PartNumber.objects.get(slug=self.kwargs['pn_slug'])
carriers = pn.carrier_set.all()
form.fields['carrier'].queryset = carriers
return form
Another way to do it would be to use get_form_kwargs:
def get_form_kwargs(self):
kwargs = super(MovementCreate, self).get_form_kwargs()
kwargs['pn_slug'] = self.kwargs.get("pn_slug")
return kwargs
Then, in the form's __init__, set the queryset:
class MovementForm(forms.ModelForm):
class Meta:
model = Movement
def __init__(self, *args, **kwargs):
pn_slug = kwargs.pop('pn_slug')
super(MovementForm, self).__init__(*args, **kwargs)
pn = PartNumber.objects.get(slug=pn_slug)
carriers = pn.carrier_set.all()
self.fields['carrier'].queryset = carriers
Personally, I would prefer the first method as it is less code.