1 from django.db import models

     2 

     3 class Poll(models.Model):

     4     question = models.CharField(maxlength=200)

     5 

     6     def __str__(self):

     7         return "Q: %s " % self.question

     8 

     9 class Choice(models.Model):

    10     poll = models.ForeignKey(Poll)

    11     choice = models.CharField(maxlength=200)

    12 

    13     def __str__(self):

    14         return "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 (=NULL in sql)

    28 >>> Choice.objects.filter(id__exact=None)

    29 []

    30 

    31 # Valid query, but fails because foo isn't a keyword

    32 >>> Choice.objects.filter(foo__exact=None) 

    33 Traceback (most recent call last):

    34 ...

    35 TypeError: Cannot resolve keyword 'foo' into field

    36 

    37 # Can't use None on anything other than __exact

    38 >>> Choice.objects.filter(id__gt=None)

    39 Traceback (most recent call last):

    40 ...

    41 ValueError: Cannot use None as a query value

    42 

    43 # Can't use None on anything other than __exact

    44 >>> Choice.objects.filter(foo__gt=None)

    45 Traceback (most recent call last):

    46 ...

    47 ValueError: Cannot use None as a query value

    48 

    49 # Related managers use __exact=None implicitly if the object hasn't been saved.

    50 >>> p2 = Poll(question="How?")

    51 >>> p2.choice_set.all()

    52 []

    53 

    54 """}