33 lines
994 B
Python
33 lines
994 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.db import models
|
||
|
from django.utils.encoding import python_2_unicode_compatible
|
||
|
|
|
||
|
|
||
|
|
@python_2_unicode_compatible
|
||
|
|
class Category(models.Model):
|
||
|
name = models.CharField(max_length=20)
|
||
|
|
parent = models.ForeignKey('self', blank=True, null=True, related_name='child_set')
|
||
|
|
|
||
|
|
def __str__(self):
|
||
|
|
return self.name
|
||
|
|
|
||
|
|
@python_2_unicode_compatible
|
||
|
class Person(models.Model):
|
||
|
|
full_name = models.CharField(max_length=20)
|
||
|
|
mother = models.ForeignKey('self', null=True, related_name='mothers_child_set')
|
||
|
|
father = models.ForeignKey('self', null=True, related_name='fathers_child_set')
|
||
|
|
|
||
|
|
def __str__(self):
|
||
|
|
return self.full_name
|