Validating blank django form field not working - django

Question

I always use the following code to validate a form to prevent blank form submission. It always works in Django 1.8 but for some reason is not working in Django 2.2.
Here is the form
class CreateForm(forms.ModelForm):
class Meta:
model = Device
fields = ['category', 'item_name', 'quantity']
def clean_category(self):
category = self.cleaned_data.get('category')
if category == '':
raise forms.ValidationError('This field is required')
return category
def clean_item_name(self):
item_name = self.cleaned_data.get('item_name')
if item_name == '':
raise forms.ValidationError('This field is required')
return item_name
Here is the model
class Device(models.Model):
category = models.CharField(max_length=50, blank=True, null=True)
item_name = models.CharField(max_length=50, blank=True, null=True)
quantity = models.IntegerField(default='0', blank=False, null=True)
Thanks

Answer 1

I think the problem is that you did not check fro None, but nevertheless. I think you aim to do too much work yourself. You can just specify that the field is required=True [Django-doc], this will:
By default, each Field class assumes the value is required, so if you pass an empty value – either None or the empty string ("") – then clean() will raise a ValidationError exception.
So we can make the fields required with:
class CreateForm(forms.ModelForm):
category = forms.CharField(required=True, max_length=50)
item_name = forms.CharField(required=True, max_length=50)
class Meta:
model = Device
fields = ['category', 'item_name', 'quantity']
That being said, it is rather "odd" to specify blank=True [Django-doc] since this actually means that the field is not required in model forms. blank=True does not mean that the empty string is allowed, since even with blank=False, you can store empty strings in the field. A ModelForm will define (most of) its validation based on the model it "wraps", so that means that if you define the model better, you remove a lot of boilerplate code. Therefore I would advise eliminating blank=True.

Answer 2

Since you are specifying these fields as blank=True and null=True in your model so change those attributes
class Device(models.Model):
category = models.CharField(max_length=50, blank=False, null=False)
Or by default if you don't specify these blank and null attribute then it will be false by default so this should work also
class Device(models.Model):
category = models.CharField(max_length=50)
EDIT based on the comment:
Like the Willem said you need to check for None.You can do like this.
def clean_category(self):
category = self.cleaned_data.get('category')
if not category:
raise forms.ValidationError('This field is required')
return category