EnglishURLField

fields.py

from django.db.models import CharField
from django.utils.text import slugify

import logging

logger = logging.getLogger(__name__)


class EnglishURLField(CharField):
    def __init__(self, *args, **kwargs):
        kwargs['max_length'] = kwargs.get('max_length', 2000)
        kwargs['db_index'] = kwargs.get('db_index', True)
        kwargs['unique'] = kwargs.get('unique', True)

        self.populate_from = kwargs.pop('populate_from', None)

        super(EnglishURLField, self).__init__(*args, **kwargs)

    def pre_save(self, model_instance, add):
        if getattr(model_instance, 'id', None):
            # try to get previous slug/URL
            current_page = model_instance.__class__.objects.get(id=model_instance.id)
            previous_slug = getattr(current_page, self.name, None)
            new_slug = getattr(model_instance, self.name, None)

            if previous_slug and new_slug and previous_slug != new_slug:
                assert type(new_slug) == str, 'slug is not a str!'
                return new_slug
            elif new_slug:
                assert type(new_slug) == str, 'slug is not a str!'
                return new_slug

        slug_value = self.value_from_object(model_instance)
        populate_from_field_value = getattr(model_instance, self.populate_from, None)

        if not slug_value and populate_from_field_value:
            slug_parts = [] if getattr(model_instance, self.populate_from, None) else []
            for parent in model_instance.get_ascendants():
                parent_name = getattr(parent, self.populate_from, None)
                if parent_name:
                    slug_parts.insert(0, slugify(parent_name))
                    logger.debug("Slugified parent {0} to {1}".format(parent, parent_name))
                else:
                    logger.debug("Parent {0} has no appropriate field or it is empty!".format(parent))

            final_slug = "/".join(slug_parts)

            return final_slug