django-eav2/fields.py

#!/usr/bin/env python
# vim: ai ts=4 sts=4 et sw=4 coding=utf-8
#
#    This software is derived from EAV-Django originally written and 
#    copyrighted by Andrey Mikhaylenko <http://pypi.python.org/pypi/eav-django>
#
#    This is free software: you can redistribute it and/or modify
#    it under the terms of the GNU Lesser General Public License as published
#    by the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This software is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU Lesser General Public License for more details.
#
#    You should have received a copy of the GNU Lesser General Public License
#    along with EAV-Django.  If not, see <http://gnu.org/licenses/>.

import uuid
import re

from django.db import models
from django.utils.translation import ugettext_lazy as _
from django.core.exceptions import ValidationError


class EavSlugField(models.SlugField):
        
    def validate(self, value, instance):
        """
            Slugs are used to convert the Python attribute name to a database
            lookup and vice versa. We need it to be a valid Python identifier.
            We don't want it to start with a '_', underscore will be used
            var variables we don't want to be saved in db.
        """
        super(EavSlugField, self).validate(value, instance)
        slug_regex = r'[a-z][a-z0-9_]*'
        if not re.match(slug_regex, value):
            raise ValidationError(_(u"Must be all lower case, "\
                                    u"start with a letter, and contain "\
                                    u"only letters, numbers, or underscores."))

    @staticmethod
    def create_slug_from_name(name):
        '''
        Creates a slug based on the name
        '''
        name = name.strip().lower()

        # Change spaces to underscores
        name = '_'.join(name.split())

        # Remove non alphanumeric characters
        return re.sub('[^\w]', '', name)


class EavDatatypeField(models.CharField):
    """
        This holds checks for the attributes datatypes.
    """

    def validate(self, value, instance):
        """
            We don't want them to be able to change the attribute type
            once it have been created.
        """
        super(EavDatatypeField, self).validate(value, instance)
        from .models import Attribute
        if not instance.pk:
            return
        if instance.value_set.count():
            raise ValidationError(_(u"You cannot change the datatype of an "
                                    u"attribute that is already in use."))