django/tests/testapp/models/many_to_one_null.py

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]
"""