karmaworld/settings/manual_unique_together.py

   1 from django.conf import settings
   2 from django.db.models import signals, FieldDoesNotExist
   3 from django.utils.text import get_text_list
   4 from django.db import IntegrityError
   5 from django.utils.translation import ugettext as _
   6
   7 # This little gem is borrowed from
   8 # https://djangosnippets.org/snippets/1628/
   9
  10 def check_unique_together(sender, **kwargs):
  11     """
  12     Check models unique_together manually. Django enforced unique together only the database level, but
  13     some databases (e.g. SQLite) doesn't support this.
  14
  15     usage:
  16         from django.db.models import signals
  17         signals.pre_save.connect(check_unique_together, sender=MyModelClass)
  18
  19     or use auto_add_check_unique_together(), see below
  20     """
  21     instance = kwargs["instance"]
  22     for field_names in sender._meta.unique_together:
  23         model_kwargs = {}
  24         for field_name in field_names:
  25             try:
  26                 data = getattr(instance, field_name)
  27             except FieldDoesNotExist:
  28                 # e.g.: a missing field, which is however necessary.
  29                 # The real exception on model creation should be raised.
  30                 continue
  31             model_kwargs[field_name] = data
  32
  33         query_set = sender.objects.filter(**model_kwargs)
  34         if instance.pk != None:
  35             # Exclude the instance if it was saved in the past
  36             query_set = query_set.exclude(pk=instance.pk)
  37
  38         count = query_set.count()
  39         if count > 0:
  40             field_names = get_text_list(field_names, _('and'))
  41             msg = _(u"%(model_name)s with this %(field_names)s already exists.") % {
  42                 'model_name': unicode(instance.__class__.__name__),
  43                 'field_names': unicode(field_names)
  44             }
  45             raise IntegrityError(msg)
  46
  47 def auto_add_check_unique_together(model_class):
  48     """
  49     Add only the signal handler check_unique_together, if a database without UNIQUE support is used.
  50     """
  51     if 'sqlite' in settings.DATABASES['default']['ENGINE']:
  52         signals.pre_save.connect(check_unique_together, sender=model_class)
  53