mirror of https://github.com/django/django.git
74 lines
2.0 KiB
Python
74 lines
2.0 KiB
Python
"""
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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 reporters, and each
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article-reporter combination (a "Writer") has a "position" field, which
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specifies the reporter's position for the given article (e.g. "Staff writer").
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"""
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from django.core import meta
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class Reporter(meta.Model):
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fields = (
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meta.CharField('first_name', maxlength=30),
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meta.CharField('last_name', maxlength=30),
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)
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def __repr__(self):
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return "%s %s" % (self.first_name, self.last_name)
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class Article(meta.Model):
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fields = (
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meta.CharField('headline', maxlength=100),
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meta.DateField('pub_date'),
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)
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def __repr__(self):
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return self.headline
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class Writer(meta.Model):
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fields = (
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meta.ForeignKey(Reporter),
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meta.ForeignKey(Article),
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meta.CharField('position', maxlength=100),
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)
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def __repr__(self):
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return '%r (%s)' % (self.get_reporter(), self.position)
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API_TESTS = """
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# Create a few Reporters.
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>>> r1 = reporters.Reporter(id=None, first_name='John', last_name='Smith')
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>>> r1.save()
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>>> r2 = reporters.Reporter(id=None, 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 = articles.Article(id=None, 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 = writers.Writer(id=None, reporter_id=r1.id, article_id=a.id, position='Main writer')
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>>> w1.save()
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>>> w2 = writers.Writer(id=None, reporter_id=r2.id, article_id=a.id, position='Contributor')
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>>> w2.save()
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# Play around with the API.
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>>> a.get_writer_list(order_by=['-position'], select_related=True)
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[John Smith (Main writer), Jane Doe (Contributor)]
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>>> w1.get_reporter()
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John Smith
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>>> w2.get_reporter()
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Jane Doe
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>>> w1.get_article()
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This is a test
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>>> w2.get_article()
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This is a test
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>>> r1.get_writer_list()
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[John Smith (Main writer)]
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"""
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