Add field validations to the model

django_field_validation.py

from django.db import models
from django.core.exceptions import ValidationError
from django.forms import ModelForm


class CleanModel(models.Model):
    """ Abstract class that adds field validations """
    
    def clean_fields(self, exclude):
        errors = {}
        try:
            super(CleanModel, self).clean_fields(exclude)
        except ValidationError, e:
            errors = e.update_error_dict(errors)

        for f in self._meta.fields:
            if hasattr(self, "clean_%s" % f.name):
                try:
                    value = getattr(self, "clean_%s" % f.name)()
                    setattr(self, f.name, value)
                except ValidationError, e:
                    errors = ValidationError({ f.name: e.messages }).update_error_dict(errors)
        if errors:
            raise ValidationError(errors)

    def is_valid(self):
        return not self.errors

    @property
    def errors(self):
        try:
            self.full_clean()
        except ValidationError, e:
            return e.update_error_dict({})
        return []

class MyModel(CleanModel):
    """ Example model with field validations """

    my_field = models.CharField(max_length=100)

    def clean_my_field(self):
        if not self.my_field or len(self.my_field) < 10:
            raise ValidationError("My Field is too short")
        return self.my_field

class MyForm(ModelForm):
    """ Example form with field validations in the model """

    class Meta:
        model = MyModel



my_object = MyModel()

my_object.is_valid()
#=> False

my_object.errors
#=> {'my_field': [u'This field cannot be null.', u'My Field is too short']}


my_object = MyModel(my_field='a')

my_object.is_valid()
#=> False

my_object.errors
#=> {'my_field': [u'My Field is too short']}


my_object = MyModel(my_field="i'm very valid")

my_object.is_valid()
#=> True


my_form = MyForm({})

my_form.is_valid()
#=> False

my_form.errors
#=> {'my_field': [u'This field is required.', u'My Field is too short']}


my_form = MyForm({ 'my_field': "I'm very valid" })

My_form.is_valid()
#=> True