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"""
34. 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 __future__ import unicode_literals
from django.contrib.contenttypes import generic
from django.contrib.contenttypes.models import ContentType
from django.db import models
from django.utils.encoding import python_2_unicode_compatible
@python_2_unicode_compatible
class TaggedItem(models.Model):
"""A tag on an item."""
tag = models.SlugField()
content_type = models.ForeignKey(ContentType)
object_id = models.PositiveIntegerField()
content_object = generic.GenericForeignKey()
class Meta:
ordering = ["tag", "content_type__name"]
def __str__(self):
return self.tag
class ValuableTaggedItem(TaggedItem):
value = models.PositiveIntegerField()
@python_2_unicode_compatible
class Comparison(models.Model):
"""
A model that tests having multiple GenericForeignKeys
"""
comparative = models.CharField(max_length=50)
content_type1 = models.ForeignKey(ContentType, related_name="comparative1_set")
object_id1 = models.PositiveIntegerField()
content_type2 = models.ForeignKey(ContentType, related_name="comparative2_set")
object_id2 = models.PositiveIntegerField()
first_obj = generic.GenericForeignKey(ct_field="content_type1", fk_field="object_id1")
other_obj = generic.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)
@python_2_unicode_compatible
class Animal(models.Model):
common_name = models.CharField(max_length=150)
latin_name = models.CharField(max_length=150)
tags = generic.GenericRelation(TaggedItem)
comparisons = generic.GenericRelation(Comparison,
object_id_field="object_id1",
content_type_field="content_type1")
def __str__(self):
return self.common_name
@python_2_unicode_compatible
class Vegetable(models.Model):
name = models.CharField(max_length=150)
is_yucky = models.BooleanField(default=True)
tags = generic.GenericRelation(TaggedItem)
def __str__(self):
return self.name
@python_2_unicode_compatible
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_query_set(self):
return super(GeckoManager, self).get_query_set().filter(has_tail=True)
class Gecko(models.Model):
has_tail = models.BooleanField()
objects = GeckoManager()
# To test fix for #11263
class Rock(Mineral):
tags = generic.GenericRelation(TaggedItem)
|
