not able to save data in django form - django

Question

I am getting error Cannot assign "'1'": "dropdown.drp1" must be a "basedrop" instance. I am sharing my code. Kindly help. I got some solutions on stack but I did not understand how to implement that in my case. Django error. Cannot assign must be an instance
models.py
class basedrop(models.Model):
name = models.CharField(max_length=50,blank=False,null=False)
def __str__(self):
return self.name
class subdrop(models.Model):
name = models.CharField(max_length=100,blank=False,null=False)
bsdrop = models.ForeignKey(basedrop,null=False,blank=False,on_delete=models.CASCADE)
def __str__(self):
return self.name
class lastdrop(models.Model):
name = models.CharField(max_length=100,blank=False,null=False)
sbdrop = models.ForeignKey(subdrop,null=False,blank=False,on_delete=models.CASCADE)
def __str__(self):
return self.name
class dropdown(models.Model):
name = models.CharField(max_length=50)
drp1 = models.ForeignKey(basedrop,max_length=50,on_delete=models.CASCADE)
drp2 = models.ForeignKey(subdrop,max_length=50,on_delete=models.CASCADE)
drp3 = models.ForeignKey(lastdrop,max_length=50,on_delete=models.CASCADE)
def __str__(self):
return self.name
views.py
def create_drop(request):
if request.method == 'POST':
form = dropdownForm(request.POST or None)
if form.is_valid():
form = dropdown(name=request.POST.get('name'),drp1_Id=int(request.POST.get('drp1')),
drp2_Id=int(request.POST.get('drp2')),drp3_Id=int(request.POST.get('drp3')))
form.save()
return HttpResponse('<p>this is working</p>')
form = dropdownForm()
return render(request,'drop.html',{'form':form})
forms.py
class dropdownForm(forms.ModelForm):
drp1 = forms.ChoiceField(choices=((bs.get('id'),bs.get('name')) for bs in basedrop.objects.all().values('id','name')))
class Meta:
model = dropdown
fields = '__all__'
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.fields['drp2'].queryset = subdrop.objects.none()
self.fields['drp3'].queryset = lastdrop.objects.none()
if 'drp1' in self.data:
try:
country_id = int(self.data.get('drp1'))
self.fields['drp2'].queryset = subdrop.objects.filter(id=country_id).order_by('name')
except (ValueError, TypeError):
pass
elif 'drp2' in self.data:
try:
country_id = int(self.data.get('drp2'))
self.fields['drp3'].queryset = lastdrop.objects.filter(id=country_id).order_by('name')
except (ValueError, TypeError):
pass
elif self.instance.pk:
self.fields['drp2'].queryset = self.instance.drp1.city_set.order_by('name')
self.fields['drp3'].queryset = self.instance.drp2.city_set.order_by('name')

Answer 1

I don't know if it could cause failures but you're passing the POSTed argument 'drp1' as integer for drp1_Id, drp2_Id and drp3_Id.
You'd have it much easier if you choose a more intuitive coding style.
For example this line:
form = dropdown(name=request.POST.get('name'), drp1_Id=int(request.POST.get('drp1')), drp2_Id=int(request.POST.get('drp1')), drp3_Id=int(request.POST.get('drp1')))
If you get the objects and pass them to the dropdown you gain readability specially if there is an error:
drp1_pk = request.POST.get('drp1')
drp1 = basedrop.objects.get(pk=drp1_pk)
drp2 = subdrop.objects.get(pk=drp1_pk)
drp3 = lastdrop.objects.get(pk=drp1_pk)
form = dropdown(name=request.POST.get('name'), drp1=drp1, drp2=drp2, drp3=drp3)
But again:
It looks strange to pass the same primary key to three different models.