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"""
11. Relating an object to itself, many-to-one
To define a many-to-one relationship between a model and itself, use
``ForeignKey('self')``.
In this example, a ``Category`` is related to itself. That is, each
``Category`` has a parent ``Category``.
Set ``related_name`` to designate what the reverse relationship is called.
"""
from django.core import meta
class Category(meta.Model):
name = meta.CharField(maxlength=20)
parent = meta.ForeignKey('self', null=True, related_name='child')
class META:
module_name = 'categories'
def __repr__(self):
return self.name
API_TESTS = """
# Create a few Category objects.
>>> r = categories.Category(id=None, name='Root category', parent=None)
>>> r.save()
>>> c = categories.Category(id=None, name='Child category', parent=r)
>>> c.save()
>>> r.get_child_list()
[Child category]
>>> r.get_child(name__startswith='Child')
Child category
>>> r.get_parent()
Traceback (most recent call last):
...
CategoryDoesNotExist
>>> c.get_child_list()
[]
>>> c.get_parent()
Root category
"""
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