"""

9. Many-to-many relationships via an intermediary table

For many-to-many relationships that need extra fields on the intermediary

table, use an intermediary model.

In this example, an ``Article`` can have multiple ``Reporter``s, and each

``Article``-``Reporter`` combination (a ``Writer``) has a ``position`` field,

which specifies the ``Reporter``'s position for the given article (e.g. "Staff

writer").

"""

from django.db import models

class Reporter(models.Model):

    first_name = models.CharField(maxlength=30)

    last_name = models.CharField(maxlength=30)

    def __str__(self):

        return "%s %s" % (self.first_name, self.last_name)

class Article(models.Model):

    headline = models.CharField(maxlength=100)

    pub_date = models.DateField()

    def __str__(self):

        return self.headline

class Writer(models.Model):

    reporter = models.ForeignKey(Reporter)

    article = models.ForeignKey(Article)

    position = models.CharField(maxlength=100)

    def __str__(self):

        return '%s (%s)' % (self.reporter, self.position)

__test__ = {'API_TESTS':"""

# Create a few Reporters.

>>> r1 = Reporter(first_name='John', last_name='Smith')

>>> r1.save()

>>> r2 = Reporter(first_name='Jane', last_name='Doe')

>>> r2.save()

# Create an Article.

>>> from datetime import datetime

>>> a = Article(headline='This is a test', pub_date=datetime(2005, 7, 27))

>>> a.save()

# Create a few Writers.

>>> w1 = Writer(reporter=r1, article=a, position='Main writer')

>>> w1.save()

>>> w2 = Writer(reporter=r2, article=a, position='Contributor')

>>> w2.save()

# Play around with the API.

>>> a.writer_set.select_related().order_by('-position')

[<Writer: John Smith (Main writer)>, <Writer: Jane Doe (Contributor)>]

>>> w1.reporter

<Reporter: John Smith>

>>> w2.reporter

<Reporter: Jane Doe>

>>> w1.article

<Article: This is a test>

>>> w2.article

<Article: This is a test>

>>> r1.writer_set.all()

[<Writer: John Smith (Main writer)>]

"""}