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git-svn-id: http://code.djangoproject.com/svn/django/branches/magic-removal@2251 bcc190cf-cafb-0310-a4f2-bffc1f526a37
43 lines
985 B
Python
43 lines
985 B
Python
"""
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11. Relating an object to itself, many-to-one
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To define a many-to-one relationship between a model and itself, use
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``ForeignKey('self')``.
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In this example, a ``Category`` is related to itself. That is, each
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``Category`` has a parent ``Category``.
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Set ``related_name`` to designate what the reverse relationship is called.
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"""
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from django.db import models
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class Category(models.Model):
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name = models.CharField(maxlength=20)
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parent = models.ForeignKey('self', null=True, related_name='child_set')
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def __repr__(self):
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return self.name
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API_TESTS = """
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# Create a few Category objects.
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>>> r = Category(id=None, name='Root category', parent=None)
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>>> r.save()
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>>> c = Category(id=None, name='Child category', parent=r)
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>>> c.save()
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>>> r.child_set.all()
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[Child category]
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>>> r.child_set.get(name__startswith='Child')
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Child category
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>>> r.parent
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Traceback (most recent call last):
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...
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DoesNotExist
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>>> c.child_set.all()
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[]
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>>> c.parent
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Root category
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"""
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