57 lines
1.7 KiB
Python
57 lines
1.7 KiB
Python
"""
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25. Reverse lookups
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This demonstrates the reverse lookup features of the database API.
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"""
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from django.db import models
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class User(models.Model):
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name = models.CharField(maxlength=200)
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def __repr__(self):
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return self.name
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class Poll(models.Model):
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question = models.CharField(maxlength=200)
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creator = models.ForeignKey(User)
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def __repr__(self):
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return self.question
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class Choice(models.Model):
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name = models.CharField(maxlength=100)
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poll = models.ForeignKey(Poll, related_name="poll_choice")
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related_poll = models.ForeignKey(Poll, related_name="related_choice")
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def __repr(self):
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return self.name
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API_TESTS = """
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>>> john = User(name="John Doe")
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>>> john.save()
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>>> jim = User(name="Jim Bo")
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>>> jim.save()
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>>> first_poll = Poll(question="What's the first question?", creator=john)
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>>> first_poll.save()
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>>> second_poll = Poll(question="What's the second question?", creator=jim)
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>>> second_poll.save()
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>>> new_choice = Choice(poll=first_poll, related_poll=second_poll, name="This is the answer.")
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>>> new_choice.save()
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>>> # Reverse lookups by field name:
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>>> User.objects.get(poll__question__exact="What's the first question?")
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John Doe
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>>> User.objects.get(poll__question__exact="What's the second question?")
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Jim Bo
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>>> # Reverse lookups by related_name:
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>>> Poll.objects.get(poll_choice__name__exact="This is the answer.")
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What's the first question?
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>>> Poll.objects.get(related_choice__name__exact="This is the answer.")
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What's the second question?
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>>> # If a related_name is given you can't use the field name instead:
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>>> Poll.objects.get(choice__name__exact="This is the answer")
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Traceback (most recent call last):
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...
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TypeError: Cannot resolve keyword 'choice' into field
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"""
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