mirror of
https://github.com/django/django.git
synced 2024-12-25 18:46:22 +00:00
49 lines
1.2 KiB
Python
49 lines
1.2 KiB
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``.
|
||
|
|
|
||
|
|
Because of this recursive relationship, we need to tell Django what the
|
||
|
|
relationships should be called. Set ``rel_name`` for this, and set
|
||
|
|
``related_name`` to designate what the reverse relationship is called.
|
||
|
|
"""
|
||
|
|
|
||
|
|
from django.core import meta
|
||
|
|
|
||
|
|
class Category(meta.Model):
|
||
|
|
module_name = 'categories'
|
||
|
|
fields = (
|
||
|
|
meta.CharField('name', maxlength=20),
|
||
|
|
meta.ForeignKey('self', null=True,
|
||
|
|
rel_name='parent', related_name='child'),
|
||
|
|
)
|
||
|
|
|
||
|
|
def __repr__(self):
|
||
|
|
return self.name
|
||
|
|
|
||
|
|
API_TESTS = """
|
||
|
|
# Create a few Category objects.
|
||
|
|
>>> r = categories.Category(id=None, name='Root category', parent_id=None)
|
||
|
|
>>> r.save()
|
||
|
|
>>> c = categories.Category(id=None, name='Child category', parent_id=r.id)
|
||
|
|
>>> 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
|
||
|
|
"""
|