mirror of
https://github.com/django/django.git
synced 2024-12-25 10:35:48 +00:00
75b5372a8f
git-svn-id: http://code.djangoproject.com/svn/django/trunk@558 bcc190cf-cafb-0310-a4f2-bffc1f526a37
79 lines
1.7 KiB
Python
79 lines
1.7 KiB
Python
"""
|
|
16. Many-to-one relationships that can be null
|
|
|
|
To define a many-to-one relationship that can have a null foreign key, use
|
|
``ForeignKey()`` with ``null=True`` .
|
|
"""
|
|
|
|
from django.core import meta
|
|
|
|
class Reporter(meta.Model):
|
|
name = meta.CharField(maxlength=30)
|
|
|
|
def __repr__(self):
|
|
return self.name
|
|
|
|
class Article(meta.Model):
|
|
headline = meta.CharField(maxlength=100)
|
|
reporter = meta.ForeignKey(Reporter, null=True)
|
|
|
|
def __repr__(self):
|
|
return self.headline
|
|
|
|
API_TESTS = """
|
|
# Create a Reporter.
|
|
>>> r = reporters.Reporter(name='John Smith')
|
|
>>> r.save()
|
|
|
|
# Create an Article.
|
|
>>> a = articles.Article(headline="First", reporter=r)
|
|
>>> a.save()
|
|
|
|
>>> a.reporter_id
|
|
1
|
|
|
|
>>> a.get_reporter()
|
|
John Smith
|
|
|
|
# Article objects have access to their related Reporter objects.
|
|
>>> r = a.get_reporter()
|
|
|
|
# Create an Article via the Reporter object.
|
|
>>> a2 = r.add_article(headline="Second")
|
|
>>> a2
|
|
Second
|
|
>>> a2.reporter_id
|
|
1
|
|
|
|
# Reporter objects have access to their related Article objects.
|
|
>>> r.get_article_list(order_by=['headline'])
|
|
[First, Second]
|
|
>>> r.get_article(headline__startswith='Fir')
|
|
First
|
|
>>> r.get_article_count()
|
|
2
|
|
|
|
# Create an Article with no Reporter by passing "reporter=None".
|
|
>>> a3 = articles.Article(headline="Third", reporter=None)
|
|
>>> a3.save()
|
|
>>> a3.id
|
|
3
|
|
>>> a3.reporter_id
|
|
>>> print a3.reporter_id
|
|
None
|
|
>>> a3 = articles.get_object(pk=3)
|
|
>>> print a3.reporter_id
|
|
None
|
|
|
|
# An article's get_reporter() method throws ReporterDoesNotExist
|
|
# if the reporter is set to None.
|
|
>>> a3.get_reporter()
|
|
Traceback (most recent call last):
|
|
...
|
|
ReporterDoesNotExist
|
|
|
|
# To retrieve the articles with no reporters set, use "reporter__isnull=True".
|
|
>>> articles.get_list(reporter__isnull=True)
|
|
[Third]
|
|
"""
|