tests/regressiontests/null_queries/models.py

   1 from django.db import models
   2
   3 class Poll(models.Model):
   4     question = models.CharField(max_length=200)
   5
   6     def __unicode__(self):
   7         return u"Q: %s " % self.question
   8
   9 class Choice(models.Model):
  10     poll = models.ForeignKey(Poll)
  11     choice = models.CharField(max_length=200)
  12
  13     def __unicode__(self):
  14         return u"Choice: %s in poll %s" % (self.choice, self.poll)
  15
  16 __test__ = {'API_TESTS':"""
  17 # Regression test for the use of None as a query value. None is interpreted as
  18 # an SQL NULL, but only in __exact queries.
  19 # Set up some initial polls and choices
  20 >>> p1 = Poll(question='Why?')
  21 >>> p1.save()
  22 >>> c1 = Choice(poll=p1, choice='Because.')
  23 >>> c1.save()
  24 >>> c2 = Choice(poll=p1, choice='Why Not?')
  25 >>> c2.save()
  26
  27 # Exact query with value None returns nothing ("is NULL" in sql, but every 'id'
  28 # field has a value).
  29 >>> Choice.objects.filter(choice__exact=None)
  30 []
  31
  32 Excluding the previous result returns everything.
  33 >>> Choice.objects.exclude(choice=None).order_by('id')
  34 [<Choice: Choice: Because. in poll Q: Why? >, <Choice: Choice: Why Not? in poll Q: Why? >]
  35
  36 # Valid query, but fails because foo isn't a keyword
  37 >>> Choice.objects.filter(foo__exact=None)
  38 Traceback (most recent call last):
  39 ...
  40 FieldError: Cannot resolve keyword 'foo' into field. Choices are: choice, id, poll
  41
  42 # Can't use None on anything other than __exact
  43 >>> Choice.objects.filter(id__gt=None)
  44 Traceback (most recent call last):
  45 ...
  46 ValueError: Cannot use None as a query value
  47
  48 # Can't use None on anything other than __exact
  49 >>> Choice.objects.filter(foo__gt=None)
  50 Traceback (most recent call last):
  51 ...
  52 ValueError: Cannot use None as a query value
  53
  54 # Related managers use __exact=None implicitly if the object hasn't been saved.
  55 >>> p2 = Poll(question="How?")
  56 >>> p2.choice_set.all()
  57 []
  58
  59 """}