author | Sverre Rabbelier <srabbelier@gmail.com> |
Thu, 02 Apr 2009 23:05:31 +0000 | |
changeset 2056 | bbd16a156bde |
parent 109 | 620f9b141567 |
permissions | -rwxr-xr-x |
109
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
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""" |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
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11. Relating an object to itself, many-to-one |
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Todd Larsen <tlarsen@google.com>
parents:
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
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To define a many-to-one relationship between a model and itself, use |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
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``ForeignKey('self')``. |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
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Todd Larsen <tlarsen@google.com>
parents:
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In this example, a ``Category`` is related to itself. That is, each |
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parents:
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``Category`` has a parent ``Category``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
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Set ``related_name`` to designate what the reverse relationship is called. |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
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""" |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
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parents:
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from django.db import models |
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parents:
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|
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class Category(models.Model): |
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name = models.CharField(maxlength=20) |
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parents:
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parent = models.ForeignKey('self', null=True, related_name='child_set') |
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parents:
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|
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def __str__(self): |
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return self.name |
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parents:
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|
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__test__ = {'API_TESTS':""" |
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parents:
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# Create a few Category objects. |
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parents:
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>>> r = Category(id=None, name='Root category', parent=None) |
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parents:
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>>> r.save() |
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parents:
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>>> c = Category(id=None, name='Child category', parent=r) |
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parents:
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>>> c.save() |
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parents:
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|
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>>> r.child_set.all() |
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parents:
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[<Category: Child category>] |
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parents:
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>>> r.child_set.get(name__startswith='Child') |
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parents:
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<Category: Child category> |
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parents:
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>>> print r.parent |
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parents:
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None |
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parents:
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|
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parents:
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>>> c.child_set.all() |
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parents:
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[] |
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parents:
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>>> c.parent |
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parents:
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<Category: Root category> |
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Todd Larsen <tlarsen@google.com>
parents:
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"""} |