Question

As the built in validator in django accepts even if just spaces are input into a field. I want a validation in which if only spaces are fed then it must raise a validation error. I have a field like this:

name = forms.CharField(max_length=200)  

Using validators outside i.e. writing a function like this works.

def validate_spaces(value):
  if value.strip() == '':
     raise ValidationError(u"You must provide more than just whitespace.")

But, I was thinking if it could be done using the form.clean() methods, i.e. without writing any extra functions outside. Any help will be much appreciated.

Answer 1

You can add custom behaviour to form.clean() this way:

class YourForm(forms.Form):
    # Everything as before.
    ...

    def clean_name(self):
        data = self.cleaned_data['name']
        if data.strip() == '':
            raise forms.ValidationError(u"You must provide more than just whitespace.")

        # Always return the cleaned data, whether you have changed it or
        # not.
        return data

However, if you want to create a type of field that automatically gets this type of validation, you add a new class like this

class NoSpacesCharField(forms.CharField):
    def validate(self, value):
        # Use the parent's handling of required fields, etc.
        super(NoSpacesCharField, self).validate(value)

        if value.strip() == '':
            raise ValidationError(u"You must provide more than just whitespace.")

Then uses NoSpacesCharField like you would ordinarily use forms.CharField.

I’m not currently in a position to test this code so there might be the odd kink in it, but it should get you most of the way there. For further info on form validation in Django see https://docs.djangoproject.com/en/dev/ref/forms/validation/