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38 lines
919 B
Python
38 lines
919 B
Python
"""
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Many-to-one relationships that can be null
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To define a many-to-one relationship that can have a null foreign key, use
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``ForeignKey()`` with ``null=True`` .
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"""
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from django.db import models
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from django.utils.encoding import python_2_unicode_compatible
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@python_2_unicode_compatible
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class Reporter(models.Model):
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name = models.CharField(max_length=30)
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def __str__(self):
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return self.name
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@python_2_unicode_compatible
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class Article(models.Model):
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headline = models.CharField(max_length=100)
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reporter = models.ForeignKey(Reporter, models.SET_NULL, null=True)
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class Meta:
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ordering = ('headline',)
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def __str__(self):
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return self.headline
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class Car(models.Model):
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make = models.CharField(max_length=100, null=True, unique=True)
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class Driver(models.Model):
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car = models.ForeignKey(Car, models.SET_NULL, to_field='make', null=True, related_name='drivers')
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