80 lines
1.9 KiB
Python
80 lines
1.9 KiB
Python
"""
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20. Multiple many-to-many relationships between the same two tables
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In this example, an Article can have many Categories (as "primary") and many
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Categories (as "secondary").
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Set ``related_name`` to designate what the reverse relationship is called.
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"""
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from django.db import models
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class Category(models.Model):
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name = models.CharField(maxlength=20)
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class Meta:
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ordering = ('name',)
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def __repr__(self):
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return self.name
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class Article(models.Model):
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headline = models.CharField(maxlength=50)
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pub_date = models.DateTimeField()
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primary_categories = models.ManyToManyField(Category, related_name='primary_article_set')
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secondary_categories = models.ManyToManyField(Category, related_name='secondary_article_set')
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class Meta:
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ordering = ('pub_date',)
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def __repr__(self):
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return self.headline
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API_TESTS = """
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>>> from datetime import datetime
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>>> c1 = Category(name='Sports')
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>>> c1.save()
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>>> c2 = Category(name='News')
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>>> c2.save()
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>>> c3 = Category(name='Crime')
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>>> c3.save()
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>>> c4 = Category(name='Life')
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>>> c4.save()
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>>> a1 = Article(headline='Area man steals', pub_date=datetime(2005, 11, 27))
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>>> a1.save()
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>>> a1.primary_categories.add(c2, c3)
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>>> a1.secondary_categories.add(c4)
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>>> a2 = Article(headline='Area man runs', pub_date=datetime(2005, 11, 28))
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>>> a2.save()
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>>> a2.primary_categories.add(c1, c2)
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>>> a2.secondary_categories.add(c4)
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>>> a1.primary_categories.all()
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[Crime, News]
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>>> a2.primary_categories.all()
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[News, Sports]
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>>> a1.secondary_categories.all()
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[Life]
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>>> c1.primary_article_set.all()
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[Area man runs]
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>>> c1.secondary_article_set.all()
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[]
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>>> c2.primary_article_set.all()
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[Area man steals, Area man runs]
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>>> c2.secondary_article_set.all()
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[]
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>>> c3.primary_article_set.all()
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[Area man steals]
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>>> c3.secondary_article_set.all()
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[]
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>>> c4.primary_article_set.all()
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[]
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>>> c4.secondary_article_set.all()
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[Area man steals, Area man runs]
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"""
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