Django ModelChoice Field Conditional ForeignKey - django

Question

I've surfed most of the afternoon and have been at this particular quandry for a while.
I am trying to figure out how to essentially present a foreign key as a dropdown choice if the user has driven that type of car. For example purposes and to keep this as easy as possible...
Let's say I have aCars, Manufacturers and a UserProfile model.
I have a model for Cars as so...
class Cars(models.Model):
car_name = models.CharField(max_length=80)
class = models.ForeignKey(Manufacturer,null=True,on_delete=models.DO_NOTHING,related_name='car_manufacturer')
I have a model for Manufacturers as so...
class Manufacturers(models.Model):
manu_name = models.CharField(max_length=80)
Then I have a UserProfile model....
class Userprofile(models.Model):
user = models.OneToOneField(User,on_delete=models.CASCADE)
user_name = models.CharField(max_length=80)
car_owned = models.ForeignKey(Car,null=True,on_delete=models.DO_NOTHING,related_name='car_owned')
All good so far...
I have a view where I am listing all of the Manufacturers and this works fine as well. It shows all of the manufacturers that I would expect in the form view below.
class ManufacturerForm(forms.Form):
dropdown = forms.ModelChoiceField(queryset=Manufacturer.objects.all())
def __init__(self, *args, **kwargs):
super(ManufacturerForm, self).__init__(*args, **kwargs)
self.fields['dropdown'].widget.attrs['class'] = 'choices1'
self.fields['dropdown'].empty_label = ''
I'm using the FORMVIEW below to display the form...
class ManufacturerView(LoginRequiredMixin,FormView):
form_class = ManufacturerForm
template_name = 'Directory/HTMLNAME.html'
def get_form_kwargs(self):
kwargs = super(ManufacturerView, self).get_form_kwargs()
kwargs['user'] = self.request.user
return kwargs
def form_valid(self, form):
manufacturer = form.cleaned_data['dropdown']
return HttpResponseRedirect(reverse("NAME:manufacturer",kwargs={'pk':manufacturer.pk}))
This all works fine. However, I can't figure out how to limit the manufacturer dropdown to only the cars the user has driven. I'm trying to essentially limit the dropdown display to only the manufacturers that are pertinent to the cars the user has owned based on their profile. I've researched reverse look ups and have also tried something similar to what is outlined below to solve my problem...
class ManufacturerForm(forms.Form):
dropdown = forms.ModelChoiceField(queryset=Manufacturer.objects.filter(car_manufacturer=1)
def __init__(self, *args, **kwargs):
super(ManufacturerForm, self).__init__(*args, **kwargs)
self.fields['dropdown'].widget.attrs['class'] = 'choices1'
self.fields['dropdown'].empty_label = ''
But this obviously only gives me record 1 for the Manufacturer model. I am trying to figure out how to display only the records that are relevant to an individual user based on their car_owned data. I can list all of the manufacturers and then just display the records that are relevant in a ListView, but I am trying to limit the dropdown to only where there are relevant records in a ListView. Thanks in advance for any thoughts.

Answer 1

You missed just couple of points:
1) Pass UserProfile as kwargs['user']:
kwargs['user'] = UserProfile.objects.get(user=self.request.user)
2) Add user parameter in form's __init__ signature and override dropdown.queryset there:
class ManufacturerForm(forms.Form):
dropdown = forms.ModelChoiceField(queryset=Manufacturer.objects.all())
def __init__(self, user, *args, **kwargs):
super(ManufacturerForm, self).__init__(*args, **kwargs)
self.fields['dropdown'].widget.attrs['class'] = 'choices1'
self.fields['dropdown'].empty_label = ''
self.fields['dropdown'].queryset = Manufacturer.objects.filter(car_manufacturer__car_owned=user)
Also I would like to recommend to rewrite your Car - User relationship to ManyToMany. If I understand correctly your message, User can have multiple cars:
limit the dropdown display to only the manufacturers that are
pertinent to the cars the user has owned
Also if I understand correctly, you want to track cars that user used to have (but doesn't have anymore).
If you rewrite Car - User relationship, then you won't probably have any reason to keep UserProfile model only to hold additional username. If so, your models.py should look like this:
class Manufacturer(models.Model):
name = models.CharField(max_length=80)
class Car(models.Model):
name = models.CharField(max_length=80)
klass = models.ForeignKey(Manufacturer, null=True, on_delete=models.DO_NOTHING, related_name='car_manufacturer')
owners = models.ManyToManyField(User, through='Ownership')
class Ownership(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE)
car = models.ForeignKey(Car, on_delete=models.CASCADE)
active = models.BooleanField(default=True) # True if user owns the car at the moment

Answer 2

I think it all hinges on your order and relationships between models, perhaps try adding in a ManyToMany relation between Manufacturer and Car, so one manufacturer can make many cars:
class Manufacturer(models.Model):
name = models.CharField(max_length=80)
car = models.ManyToManyField(Car)
Then it may be a case of doing something such as:
qs = Manufacturer.objects.all(car=user.car_owned)
dropdown = forms.ModelChoiceField(qs)
And in your views.py file:
form = ManufacturerForm(request.POST, user=request.user)
(You may need to look up if the above is valid, as I'm not sure if Forms can have the request object passed in).
Disclaimer: I see you're using a class based view...so I may need to tweak the above.