mirror of
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919934602f
Thanks to Collin Anderson for the suggestion and Tim Graham for
reviewing the patch.
Backport of 22c6497f99 from master
124 lines
3.8 KiB
Python
124 lines
3.8 KiB
Python
"""
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34. Generic relations
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Generic relations let an object have a foreign key to any object through a
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content-type/object-id field. A ``GenericForeignKey`` field can point to any
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object, be it animal, vegetable, or mineral.
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The canonical example is tags (although this example implementation is *far*
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from complete).
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"""
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from __future__ import unicode_literals
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from django.contrib.contenttypes import generic
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from django.contrib.contenttypes.models import ContentType
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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 TaggedItem(models.Model):
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"""A tag on an item."""
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tag = models.SlugField()
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content_type = models.ForeignKey(ContentType)
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object_id = models.PositiveIntegerField()
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content_object = generic.GenericForeignKey()
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class Meta:
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ordering = ["tag", "content_type__name"]
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def __str__(self):
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return self.tag
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class ValuableTaggedItem(TaggedItem):
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value = models.PositiveIntegerField()
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@python_2_unicode_compatible
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class Comparison(models.Model):
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"""
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A model that tests having multiple GenericForeignKeys
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"""
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comparative = models.CharField(max_length=50)
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content_type1 = models.ForeignKey(ContentType, related_name="comparative1_set")
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object_id1 = models.PositiveIntegerField()
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content_type2 = models.ForeignKey(ContentType, related_name="comparative2_set")
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object_id2 = models.PositiveIntegerField()
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first_obj = generic.GenericForeignKey(ct_field="content_type1", fk_field="object_id1")
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other_obj = generic.GenericForeignKey(ct_field="content_type2", fk_field="object_id2")
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def __str__(self):
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return "%s is %s than %s" % (self.first_obj, self.comparative, self.other_obj)
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@python_2_unicode_compatible
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class Animal(models.Model):
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common_name = models.CharField(max_length=150)
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latin_name = models.CharField(max_length=150)
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tags = generic.GenericRelation(TaggedItem)
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comparisons = generic.GenericRelation(Comparison,
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object_id_field="object_id1",
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content_type_field="content_type1")
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def __str__(self):
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return self.common_name
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@python_2_unicode_compatible
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class Vegetable(models.Model):
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name = models.CharField(max_length=150)
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is_yucky = models.BooleanField(default=True)
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tags = generic.GenericRelation(TaggedItem)
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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 Mineral(models.Model):
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name = models.CharField(max_length=150)
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hardness = models.PositiveSmallIntegerField()
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# note the lack of an explicit GenericRelation here...
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def __str__(self):
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return self.name
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class GeckoManager(models.Manager):
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def get_queryset(self):
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return super(GeckoManager, self).get_queryset().filter(has_tail=True)
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class Gecko(models.Model):
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has_tail = models.BooleanField(default=False)
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objects = GeckoManager()
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# To test fix for #11263
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class Rock(Mineral):
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tags = generic.GenericRelation(TaggedItem)
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class ManualPK(models.Model):
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id = models.IntegerField(primary_key=True)
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tags = generic.GenericRelation(TaggedItem)
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class ForProxyModelModel(models.Model):
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content_type = models.ForeignKey(ContentType)
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object_id = models.PositiveIntegerField()
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obj = generic.GenericForeignKey(for_concrete_model=False)
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title = models.CharField(max_length=255, null=True)
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class ForConcreteModelModel(models.Model):
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content_type = models.ForeignKey(ContentType)
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object_id = models.PositiveIntegerField()
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obj = generic.GenericForeignKey()
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class ConcreteRelatedModel(models.Model):
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bases = generic.GenericRelation(ForProxyModelModel, for_concrete_model=False)
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class ProxyRelatedModel(ConcreteRelatedModel):
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class Meta:
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proxy = True
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