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68 lines
1.9 KiB
68 lines
1.9 KiB
""" |
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9. Many-to-many relationships via an intermediary table |
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For many-to-many relationships that need extra fields on the intermediary |
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table, use an intermediary model. |
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In this example, an ``Article`` can have multiple ``Reporter`` objects, and |
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each ``Article``-``Reporter`` combination (a ``Writer``) has a ``position`` |
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field, which specifies the ``Reporter``'s position for the given article |
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(e.g. "Staff writer"). |
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""" |
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from django.db import models |
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class Reporter(models.Model): |
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first_name = models.CharField(max_length=30) |
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last_name = models.CharField(max_length=30) |
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def __unicode__(self): |
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return u"%s %s" % (self.first_name, self.last_name) |
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class Article(models.Model): |
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headline = models.CharField(max_length=100) |
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pub_date = models.DateField() |
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def __unicode__(self): |
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return self.headline |
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class Writer(models.Model): |
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reporter = models.ForeignKey(Reporter) |
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article = models.ForeignKey(Article) |
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position = models.CharField(max_length=100) |
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def __unicode__(self): |
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return u'%s (%s)' % (self.reporter, self.position) |
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__test__ = {'API_TESTS':""" |
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# Create a few Reporters. |
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>>> r1 = Reporter(first_name='John', last_name='Smith') |
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>>> r1.save() |
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>>> r2 = Reporter(first_name='Jane', last_name='Doe') |
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>>> r2.save() |
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# Create an Article. |
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>>> from datetime import datetime |
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>>> a = Article(headline='This is a test', pub_date=datetime(2005, 7, 27)) |
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>>> a.save() |
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# Create a few Writers. |
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>>> w1 = Writer(reporter=r1, article=a, position='Main writer') |
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>>> w1.save() |
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>>> w2 = Writer(reporter=r2, article=a, position='Contributor') |
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>>> w2.save() |
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# Play around with the API. |
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>>> a.writer_set.select_related().order_by('-position') |
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[<Writer: John Smith (Main writer)>, <Writer: Jane Doe (Contributor)>] |
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>>> w1.reporter |
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<Reporter: John Smith> |
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>>> w2.reporter |
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<Reporter: Jane Doe> |
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>>> w1.article |
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<Article: This is a test> |
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>>> w2.article |
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<Article: This is a test> |
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>>> r1.writer_set.all() |
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[<Writer: John Smith (Main writer)>] |
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"""}
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