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"""
Generic relations
Generic relations let an object have a foreign key to any object through a
content-type/object-id field. A ``GenericForeignKey`` field can point to any
object, be it animal, vegetable, or mineral.
The canonical example is tags (although this example implementation is *far*
from complete).
"""
from django.contrib.contenttypes.fields import (
GenericForeignKey, GenericRelation,
)
from django.contrib.contenttypes.models import ContentType
from django.db import models
class TaggedItem(models.Model):
"""A tag on an item."""
tag = models.SlugField()
content_type = models.ForeignKey(ContentType, models.CASCADE)
object_id = models.PositiveIntegerField()
content_object = GenericForeignKey()
class Meta:
ordering = ["tag", "content_type__model"]
def __str__(self):
return self.tag
class ValuableTaggedItem(TaggedItem):
value = models.PositiveIntegerField()
class AbstractComparison(models.Model):
comparative = models.CharField(max_length=50)
content_type1 = models.ForeignKey(ContentType, models.CASCADE, related_name="comparative1_set")
object_id1 = models.PositiveIntegerField()
first_obj = GenericForeignKey(ct_field="content_type1", fk_field="object_id1")
class Comparison(AbstractComparison):
"""
A model that tests having multiple GenericForeignKeys. One is defined
through an inherited abstract model and one defined directly on this class.
"""
content_type2 = models.ForeignKey(ContentType, models.CASCADE, related_name="comparative2_set")
object_id2 = models.PositiveIntegerField()
other_obj = GenericForeignKey(ct_field="content_type2", fk_field="object_id2")
def __str__(self):
return "%s is %s than %s" % (self.first_obj, self.comparative, self.other_obj)
class Animal(models.Model):
common_name = models.CharField(max_length=150)
latin_name = models.CharField(max_length=150)
tags = GenericRelation(TaggedItem, related_query_name='animal')
comparisons = GenericRelation(Comparison,
object_id_field="object_id1",
content_type_field="content_type1")
def __str__(self):
return self.common_name
class Vegetable(models.Model):
name = models.CharField(max_length=150)
is_yucky = models.BooleanField(default=True)
tags = GenericRelation(TaggedItem)
def __str__(self):
return self.name
class Carrot(Vegetable):
pass
class Mineral(models.Model):
name = models.CharField(max_length=150)
hardness = models.PositiveSmallIntegerField()
# note the lack of an explicit GenericRelation here...
def __str__(self):
return self.name
class GeckoManager(models.Manager):
def get_queryset(self):
return super().get_queryset().filter(has_tail=True)
class Gecko(models.Model):
has_tail = models.BooleanField(default=False)
objects = GeckoManager()
# To test fix for #11263
class Rock(Mineral):
tags = GenericRelation(TaggedItem)
class ValuableRock(Mineral):
tags = GenericRelation(ValuableTaggedItem)
class ManualPK(models.Model):
id = models.IntegerField(primary_key=True)
tags = GenericRelation(TaggedItem, related_query_name='manualpk')
class ForProxyModelModel(models.Model):
content_type = models.ForeignKey(ContentType, models.CASCADE)
object_id = models.PositiveIntegerField()
obj = GenericForeignKey(for_concrete_model=False)
title = models.CharField(max_length=255, null=True)
class ForConcreteModelModel(models.Model):
content_type = models.ForeignKey(ContentType, models.CASCADE)
object_id = models.PositiveIntegerField()
obj = GenericForeignKey()
class ConcreteRelatedModel(models.Model):
bases = GenericRelation(ForProxyModelModel, for_concrete_model=False)
class ProxyRelatedModel(ConcreteRelatedModel):
class Meta:
proxy = True
# To test fix for #7551
class AllowsNullGFK(models.Model):
content_type = models.ForeignKey(ContentType, models.SET_NULL, null=True)
object_id = models.PositiveIntegerField(null=True)
content_object = GenericForeignKey()
|
