43 lines
985 B
Python
43 lines
985 B
Python
|
"""
|
||
|
|
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')
|
||
|
|
|
||
|
|
def __repr__(self):
|
||
|
|
return self.name
|
||
|
|
|
||
|
|
API_TESTS = """
|
||
|
|
# Create a few Category objects.
|
||
|
|
>>> r = Category(id=None, name='Root category', parent=None)
|
||
|
|
>>> r.save()
|
||
|
|
>>> c = 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):
|
||
|
|
...
|
||
|
|
DoesNotExist
|
||
|
|
|
||
|
|
>>> c.get_child_list()
|
||
|
|
[]
|
||
|
|
>>> c.get_parent()
|
||
|
|
Root category
|
||
|
|
"""
|