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153 lines
4.0 KiB
Python
153 lines
4.0 KiB
Python
"""
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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 django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
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from django.contrib.contenttypes.models import ContentType
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from django.db import models
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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, models.CASCADE)
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object_id = models.PositiveIntegerField()
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content_object = GenericForeignKey()
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class Meta:
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ordering = ["tag", "content_type__model"]
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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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class AbstractComparison(models.Model):
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comparative = models.CharField(max_length=50)
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content_type1 = models.ForeignKey(
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ContentType, models.CASCADE, related_name="comparative1_set"
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)
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object_id1 = models.PositiveIntegerField()
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first_obj = GenericForeignKey(ct_field="content_type1", fk_field="object_id1")
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class Comparison(AbstractComparison):
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"""
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A model that tests having multiple GenericForeignKeys. One is defined
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through an inherited abstract model and one defined directly on this class.
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"""
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content_type2 = models.ForeignKey(
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ContentType, models.CASCADE, related_name="comparative2_set"
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)
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object_id2 = models.PositiveIntegerField()
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other_obj = 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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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 = GenericRelation(TaggedItem, related_query_name="animal")
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comparisons = GenericRelation(
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Comparison, object_id_field="object_id1", content_type_field="content_type1"
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)
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def __str__(self):
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return self.common_name
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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 = GenericRelation(TaggedItem)
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def __str__(self):
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return self.name
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class Carrot(Vegetable):
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pass
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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().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 = GenericRelation(TaggedItem)
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class ValuableRock(Mineral):
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tags = GenericRelation(ValuableTaggedItem)
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class ManualPK(models.Model):
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id = models.IntegerField(primary_key=True)
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tags = GenericRelation(TaggedItem, related_query_name="manualpk")
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class ForProxyModelModel(models.Model):
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content_type = models.ForeignKey(ContentType, models.CASCADE)
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object_id = models.PositiveIntegerField()
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obj = 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, models.CASCADE)
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object_id = models.PositiveIntegerField()
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obj = GenericForeignKey()
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class ConcreteRelatedModel(models.Model):
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bases = 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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# To test fix for #7551
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class AllowsNullGFK(models.Model):
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content_type = models.ForeignKey(ContentType, models.SET_NULL, null=True)
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object_id = models.PositiveIntegerField(null=True)
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content_object = GenericForeignKey()
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