mirror of
https://github.com/django/django.git
synced 2024-12-26 19:16:11 +00:00
1006d6eb06
tests for this as well. Thanks to Adam Endicott for the original patch on which this is based. git-svn-id: http://code.djangoproject.com/svn/django/trunk@2902 bcc190cf-cafb-0310-a4f2-bffc1f526a37
239 lines
7.1 KiB
Python
239 lines
7.1 KiB
Python
"""
|
|
4. Many-to-one relationships
|
|
|
|
To define a many-to-one relationship, use ``ForeignKey()`` .
|
|
"""
|
|
|
|
from django.db import models
|
|
|
|
class Reporter(models.Model):
|
|
first_name = models.CharField(maxlength=30)
|
|
last_name = models.CharField(maxlength=30)
|
|
email = models.EmailField()
|
|
|
|
def __repr__(self):
|
|
return "%s %s" % (self.first_name, self.last_name)
|
|
|
|
class Article(models.Model):
|
|
headline = models.CharField(maxlength=100)
|
|
pub_date = models.DateField()
|
|
reporter = models.ForeignKey(Reporter)
|
|
|
|
def __repr__(self):
|
|
return self.headline
|
|
|
|
class Meta:
|
|
ordering = ('headline',)
|
|
|
|
API_TESTS = """
|
|
# Create a few Reporters.
|
|
>>> r = Reporter(first_name='John', last_name='Smith', email='john@example.com')
|
|
>>> r.save()
|
|
|
|
>>> r2 = Reporter(first_name='Paul', last_name='Jones', email='paul@example.com')
|
|
>>> r2.save()
|
|
|
|
# Create an Article.
|
|
>>> from datetime import datetime
|
|
>>> a = Article(id=None, headline="This is a test", pub_date=datetime(2005, 7, 27), reporter=r)
|
|
>>> a.save()
|
|
|
|
>>> a.reporter.id
|
|
1
|
|
|
|
>>> a.reporter
|
|
John Smith
|
|
|
|
# Article objects have access to their related Reporter objects.
|
|
>>> r = a.reporter
|
|
>>> r.first_name, r.last_name
|
|
('John', 'Smith')
|
|
|
|
# Create an Article via the Reporter object.
|
|
>>> new_article = r.article_set.create(headline="John's second story", pub_date=datetime(2005, 7, 29))
|
|
>>> new_article
|
|
John's second story
|
|
>>> new_article.reporter.id
|
|
1
|
|
|
|
# Create a new article, and add it to the article set.
|
|
>>> new_article2 = Article(headline="Paul's story", pub_date=datetime(2006, 1, 17))
|
|
>>> r.article_set.add(new_article2)
|
|
>>> new_article2.reporter.id
|
|
1
|
|
>>> r.article_set.all()
|
|
[John's second story, Paul's story, This is a test]
|
|
|
|
# Add the same article to a different article set - check that it moves.
|
|
>>> r2.article_set.add(new_article2)
|
|
>>> new_article2.reporter.id
|
|
2
|
|
>>> r.article_set.all()
|
|
[John's second story, This is a test]
|
|
>>> r2.article_set.all()
|
|
[Paul's story]
|
|
|
|
# Assign the article to the reporter directly using the descriptor
|
|
>>> new_article2.reporter = r
|
|
>>> new_article2.save()
|
|
>>> new_article2.reporter
|
|
John Smith
|
|
>>> new_article2.reporter.id
|
|
1
|
|
>>> r.article_set.all()
|
|
[John's second story, Paul's story, This is a test]
|
|
>>> r2.article_set.all()
|
|
[]
|
|
|
|
# Set the article back again using set descriptor.
|
|
>>> r2.article_set = [new_article, new_article2]
|
|
>>> r.article_set.all()
|
|
[This is a test]
|
|
>>> r2.article_set.all()
|
|
[John's second story, Paul's story]
|
|
|
|
# Funny case - assignment notation can only go so far; because the
|
|
# ForeignKey cannot be null, existing members of the set must remain
|
|
>>> r.article_set = [new_article]
|
|
>>> r.article_set.all()
|
|
[John's second story, This is a test]
|
|
>>> r2.article_set.all()
|
|
[Paul's story]
|
|
|
|
# Reporter cannot be null - there should not be a clear or remove method
|
|
>>> hasattr(r2.article_set, 'remove')
|
|
False
|
|
>>> hasattr(r2.article_set, 'clear')
|
|
False
|
|
|
|
# Reporter objects have access to their related Article objects.
|
|
>>> r.article_set.all()
|
|
[John's second story, This is a test]
|
|
|
|
>>> r.article_set.filter(headline__startswith='This')
|
|
[This is a test]
|
|
|
|
>>> r.article_set.count()
|
|
2
|
|
|
|
>>> r2.article_set.count()
|
|
1
|
|
|
|
# Get articles by id
|
|
>>> Article.objects.filter(id__exact=1)
|
|
[This is a test]
|
|
>>> Article.objects.filter(pk=1)
|
|
[This is a test]
|
|
|
|
# Query on an article property
|
|
>>> Article.objects.filter(headline__startswith='This')
|
|
[This is a test]
|
|
|
|
# The API automatically follows relationships as far as you need.
|
|
# Use double underscores to separate relationships.
|
|
# This works as many levels deep as you want. There's no limit.
|
|
# Find all Articles for any Reporter whose first name is "John".
|
|
>>> Article.objects.filter(reporter__first_name__exact='John')
|
|
[John's second story, This is a test]
|
|
|
|
# Query twice over the related field.
|
|
>>> Article.objects.filter(reporter__first_name__exact='John', reporter__last_name__exact='Smith')
|
|
[John's second story, This is a test]
|
|
|
|
# The underlying query only makes one join when a related table is referenced twice.
|
|
>>> query = Article.objects.filter(reporter__first_name__exact='John', reporter__last_name__exact='Smith')
|
|
>>> null, sql, null = query._get_sql_clause()
|
|
>>> sql.count('INNER JOIN')
|
|
1
|
|
|
|
# The automatically joined table has a predictable name.
|
|
>>> Article.objects.filter(reporter__first_name__exact='John').extra(where=["many_to_one_article__reporter.last_name='Smith'"])
|
|
[John's second story, This is a test]
|
|
|
|
# Find all Articles for the Reporter whose ID is 1.
|
|
>>> Article.objects.filter(reporter__id__exact=1)
|
|
[John's second story, This is a test]
|
|
>>> Article.objects.filter(reporter__pk=1)
|
|
[John's second story, This is a test]
|
|
|
|
# You need two underscores between "reporter" and "id" -- not one.
|
|
>>> Article.objects.filter(reporter_id__exact=1)
|
|
Traceback (most recent call last):
|
|
...
|
|
TypeError: Cannot resolve keyword 'reporter_id' into field
|
|
|
|
# You need to specify a comparison clause
|
|
>>> Article.objects.filter(reporter_id=1)
|
|
Traceback (most recent call last):
|
|
...
|
|
TypeError: Cannot resolve keyword 'reporter_id' into field
|
|
|
|
# "pk" shortcut syntax works in a related context, too.
|
|
>>> Article.objects.filter(reporter__pk=1)
|
|
[John's second story, This is a test]
|
|
|
|
# You can also instantiate an Article by passing
|
|
# the Reporter's ID instead of a Reporter object.
|
|
>>> a3 = Article(id=None, headline="This is a test", pub_date=datetime(2005, 7, 27), reporter_id=r.id)
|
|
>>> a3.save()
|
|
>>> a3.reporter.id
|
|
1
|
|
>>> a3.reporter
|
|
John Smith
|
|
|
|
# Similarly, the reporter ID can be a string.
|
|
>>> a4 = Article(id=None, headline="This is a test", pub_date=datetime(2005, 7, 27), reporter_id="1")
|
|
>>> a4.save()
|
|
>>> a4.reporter
|
|
John Smith
|
|
|
|
# Reporters can be queried
|
|
>>> Reporter.objects.filter(id__exact=1)
|
|
[John Smith]
|
|
>>> Reporter.objects.filter(pk=1)
|
|
[John Smith]
|
|
>>> Reporter.objects.filter(first_name__startswith='John')
|
|
[John Smith]
|
|
|
|
# Reporters can query in opposite direction of ForeignKey definition
|
|
>>> Reporter.objects.filter(article__id__exact=1)
|
|
[John Smith]
|
|
>>> Reporter.objects.filter(article__pk=1)
|
|
[John Smith]
|
|
>>> Reporter.objects.filter(article__headline__startswith='This')
|
|
[John Smith, John Smith, John Smith]
|
|
>>> Reporter.objects.filter(article__headline__startswith='This').distinct()
|
|
[John Smith]
|
|
|
|
# Counting in the opposite direction works in conjunction with distinct()
|
|
>>> Reporter.objects.filter(article__headline__startswith='This').count()
|
|
3
|
|
>>> Reporter.objects.filter(article__headline__startswith='This').distinct().count()
|
|
1
|
|
|
|
# Queries can go round in circles.
|
|
>>> Reporter.objects.filter(article__reporter__first_name__startswith='John')
|
|
[John Smith, John Smith, John Smith, John Smith]
|
|
>>> Reporter.objects.filter(article__reporter__first_name__startswith='John').distinct()
|
|
[John Smith]
|
|
|
|
# If you delete a reporter, his articles will be deleted.
|
|
>>> Article.objects.all()
|
|
[John's second story, Paul's story, This is a test, This is a test, This is a test]
|
|
>>> Reporter.objects.order_by('first_name')
|
|
[John Smith, Paul Jones]
|
|
>>> r2.delete()
|
|
>>> Article.objects.all()
|
|
[John's second story, This is a test, This is a test, This is a test]
|
|
>>> Reporter.objects.order_by('first_name')
|
|
[John Smith]
|
|
|
|
# Deletes using a join in the query
|
|
>>> Reporter.objects.filter(article__headline__startswith='This').delete()
|
|
>>> Reporter.objects.all()
|
|
[]
|
|
>>> Article.objects.all()
|
|
[]
|
|
|
|
"""
|