Create Custom Error Messages with Model Forms

Question

I can see how to add an error message to a field when using forms, but what about model form?

This is my test model:

class Author(models.Model):
             


        

Answer 1

You can easily check and put custom error message by overriding clean()method and using self.add_error(field, message):

def clean(self):
    super(PromotionForm, self).clean()
    error_message = ''
    field = ''
    # reusable check
    if self.cleaned_data['reusable'] == 0:
        error_message = 'reusable should not be zero'
        field = 'reusable'
        self.add_error(field, error_message)
        raise ValidationError(error_message)

    return self.cleaned_data