Question

How can I add form validation and preferably with i18n localization? I tried something like the following which doesn’t work and needs to import Validationerror

class AForm(djangoforms.ModelForm):

  def clean_name(self):
      value = self.data['name']

      if not value:
        raise ValidationError("No name.")
        return self.data['name']

  def clean_email(self):
      pass

If I get it to work can I raise a localized ValidationError like this?

ValidationError(_("No name."))

Answer 1

I haven’t used the Google app engine, so the import paths are probably wrong, but the pattern I’ve used before with standard Django is:

from django import forms
from django.utils.translation import ugettext_lazy as _

class AForm(forms.ModelForm):

    def clean_name(self):
        # Get the value from the cleaned data.
        value = self.cleaned_data['name']

        # Check it exists.
        if not value:
            raise forms.ValidationError(_("No name."))

        # Return the (now validated) value.
        return self.data['name']

See the docs on field validation for further information.

Also, I presume that your actual application is more complicated than this – if you only want to check that the field is given, set the required attribute on the field and Django will do it for you.