Django unique model fields validation in form

validate_unique is a Model method.

Running the superclass clean method should take care of model uniqueness checks given a ModelForm.

class MyModelForm(forms.ModelForm):    
    def clean(self):
        cleaned_data = super(MyModelForm, self).clean()
        # additional cleaning here
        return cleaned_data

There is a warning on the django docs specifically about overriding clean on ModelForms, which automatically does several model validation steps.

simple way to achieve uniqueness to a field, just use "unique=True" in the model field. Example:

email = models.EmailField(verbose_name=_('Email'), max_length=255, unique=True)

phone = models.CharField(verbose_name=_('Phone Number'), max_length=14, unique=True)

But if you really want to achieve this through form, or situation demands it, for example, in the above code section, here phone number is a character field. uniqueness is difficult to achieve here because for the system 0171-xxxxxxx and 0171xxxxxxx are different numbers but actually they are same. It can be easily validated through form's clean_phone method. Here the digit is parsed from the string(character field) before checking uniqueness.

    def clean_phone(self):
        phone = self.cleaned_data.get("phone")
        # parse digits from the string
        digit_list = re.findall("\d+", phone)
        phone = ''.join(digit_list)
        
        if CustomUser.objects.filter(phone=phone).exists():
            raise forms.ValidationError("phone number is already exists")
        return phone

I solve it by adding validate_unique() to save()

class Server( models.Model ):
    host = models.GenericIPAddressField( blank = False, null = False, unique = True )
    name = models.CharField( blank = False, null = False, unique = True, max_length = 55 )

    def save(self, *args,**kwargs):
        self.validate_unique()
        super(Server,self).save(*args, **kwargs) 

It works for me. I don't know about you.