How to validate ModelForm with unique_together fields in Django? - django

Question

How to validate the unique_together error and how to return the custom error message to the html through the view.py. Please help.
model.py:
class Pcq(models.Model):
product = models.ForeignKey(Product, null=False)
component = models.ForeignKey(Component, null=False)
quantity = models.IntegerField('Quantity', null=False)
class Meta:
unique_together = ("product", "component")
def __unicode__(self):
return self.product.productname
Form.py
class PcqForm(ModelForm):
class Meta:
model = Pcq
fields = ['component', 'quantity']
exclude = ['product']
Views.py
def pcq_add(request, product_id):
if request.method == 'POST':
form = PcqForm(request.POST or None)
if form.is_valid():
pcq = form.save(commit=False)
pcq.product_id = product_id
pcq.save()
form = PcqForm()
successmsg = "Component added successfully! Add another Component..."
return render(request, 'maps/pcq/pcq_add.html', {'form': form, 'product_id': product_id, 'successmsg': successmsg})
form = PcqForm()
return render(request, 'maps/pcq/pcq_add.html', {'form': form, 'product_id': product_id})

Answer 1

You need a custom clean function for the form
class PcqForm(ModelForm):
class Meta:
model = Pcq
fields = ['component', 'quantity']
exclude = ['product']
def clean(self):
cleaned_data = super(PcqForm, self).clean()
component = cleaned_data.get('component')
quantity = cleaned_data.get('quantity')
if component and quantity:
try:
Pcq.objects.get(
component=component,
quantity=quantity,
)
except Pcq.DoesNotExist:
# Yay
pass
else
raise forms.ValidationError(_("Error message goes here"))
UPDATE
Same concept as above but in the view.
def pcq_add(request, product_id):
if request.method == 'POST':
form = PcqForm(request.POST or None)
data = {
'form': form,
'product_id': product_id
}
if form.is_valid():
pcq = form.save(commit=False)
pcq.product_id = product_id
try:
pcq.save()
except IntegrityError:
# You'll need to check the exception that is raised
# Handle failed unique_together
pass
else:
form = PcqForm()
data['successmsg'] = (
"Component added successfully! Add another Component.")
else:
form = PcqForm()
data = {'form': form, 'product_id': product_id}
return render(request, 'maps/pcq/pcq_add.html', data)
Alternatively:
remove the exclude = ['product']
on GET pass product_id to the form form = PcqForm(initial_data={'product': product_id})
Use the form to validate unique_together (Not sure you even need a custom clean then)