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git-svn-id: http://code.djangoproject.com/svn/django/trunk@10017 bcc190cf-cafb-0310-a4f2-bffc1f526a37
247 lines
12 KiB
Python
247 lines
12 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 django.db import models
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from django.contrib.contenttypes.models import ContentType
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from django.contrib.contenttypes import generic
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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", "-object_id"]
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def __unicode__(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 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 __unicode__(self):
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return u"%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 = 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 __unicode__(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 = generic.GenericRelation(TaggedItem)
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def __unicode__(self):
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return self.name
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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 __unicode__(self):
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return self.name
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__test__ = {'API_TESTS':"""
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# Create the world in 7 lines of code...
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>>> lion = Animal(common_name="Lion", latin_name="Panthera leo")
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>>> platypus = Animal(common_name="Platypus", latin_name="Ornithorhynchus anatinus")
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>>> eggplant = Vegetable(name="Eggplant", is_yucky=True)
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>>> bacon = Vegetable(name="Bacon", is_yucky=False)
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>>> quartz = Mineral(name="Quartz", hardness=7)
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>>> for o in (platypus, lion, eggplant, bacon, quartz):
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... o.save()
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# Objects with declared GenericRelations can be tagged directly -- the API
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# mimics the many-to-many API.
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>>> bacon.tags.create(tag="fatty")
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<TaggedItem: fatty>
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>>> bacon.tags.create(tag="salty")
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<TaggedItem: salty>
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>>> lion.tags.create(tag="yellow")
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<TaggedItem: yellow>
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>>> lion.tags.create(tag="hairy")
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<TaggedItem: hairy>
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>>> platypus.tags.create(tag="fatty")
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<TaggedItem: fatty>
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>>> lion.tags.all()
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[<TaggedItem: hairy>, <TaggedItem: yellow>]
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>>> bacon.tags.all()
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[<TaggedItem: fatty>, <TaggedItem: salty>]
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# You can easily access the content object like a foreign key.
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>>> t = TaggedItem.objects.get(tag="salty")
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>>> t.content_object
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<Vegetable: Bacon>
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# Recall that the Mineral class doesn't have an explicit GenericRelation
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# defined. That's OK, because you can create TaggedItems explicitly.
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>>> tag1 = TaggedItem(content_object=quartz, tag="shiny")
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>>> tag2 = TaggedItem(content_object=quartz, tag="clearish")
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>>> tag1.save()
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>>> tag2.save()
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# However, excluding GenericRelations means your lookups have to be a bit more
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# explicit.
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>>> from django.contrib.contenttypes.models import ContentType
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>>> ctype = ContentType.objects.get_for_model(quartz)
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>>> TaggedItem.objects.filter(content_type__pk=ctype.id, object_id=quartz.id)
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[<TaggedItem: clearish>, <TaggedItem: shiny>]
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# You can set a generic foreign key in the way you'd expect.
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>>> tag1.content_object = platypus
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>>> tag1.save()
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>>> platypus.tags.all()
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[<TaggedItem: fatty>, <TaggedItem: shiny>]
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>>> TaggedItem.objects.filter(content_type__pk=ctype.id, object_id=quartz.id)
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[<TaggedItem: clearish>]
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# Queries across generic relations respect the content types. Even though there are two TaggedItems with a tag of "fatty", this query only pulls out the one with the content type related to Animals.
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>>> Animal.objects.order_by('common_name')
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[<Animal: Lion>, <Animal: Platypus>]
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>>> Animal.objects.filter(tags__tag='fatty')
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[<Animal: Platypus>]
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>>> Animal.objects.exclude(tags__tag='fatty')
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[<Animal: Lion>]
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# If you delete an object with an explicit Generic relation, the related
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# objects are deleted when the source object is deleted.
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# Original list of tags:
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>>> [(t.tag, t.content_type, t.object_id) for t in TaggedItem.objects.all()]
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[(u'clearish', <ContentType: mineral>, 1), (u'fatty', <ContentType: vegetable>, 2), (u'fatty', <ContentType: animal>, 1), (u'hairy', <ContentType: animal>, 2), (u'salty', <ContentType: vegetable>, 2), (u'shiny', <ContentType: animal>, 1), (u'yellow', <ContentType: animal>, 2)]
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>>> lion.delete()
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>>> [(t.tag, t.content_type, t.object_id) for t in TaggedItem.objects.all()]
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[(u'clearish', <ContentType: mineral>, 1), (u'fatty', <ContentType: vegetable>, 2), (u'fatty', <ContentType: animal>, 1), (u'salty', <ContentType: vegetable>, 2), (u'shiny', <ContentType: animal>, 1)]
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# If Generic Relation is not explicitly defined, any related objects
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# remain after deletion of the source object.
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>>> quartz.delete()
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>>> [(t.tag, t.content_type, t.object_id) for t in TaggedItem.objects.all()]
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[(u'clearish', <ContentType: mineral>, 1), (u'fatty', <ContentType: vegetable>, 2), (u'fatty', <ContentType: animal>, 1), (u'salty', <ContentType: vegetable>, 2), (u'shiny', <ContentType: animal>, 1)]
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# If you delete a tag, the objects using the tag are unaffected
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# (other than losing a tag)
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>>> tag = TaggedItem.objects.get(id=1)
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>>> tag.delete()
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>>> bacon.tags.all()
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[<TaggedItem: salty>]
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>>> [(t.tag, t.content_type, t.object_id) for t in TaggedItem.objects.all()]
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[(u'clearish', <ContentType: mineral>, 1), (u'fatty', <ContentType: animal>, 1), (u'salty', <ContentType: vegetable>, 2), (u'shiny', <ContentType: animal>, 1)]
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>>> TaggedItem.objects.filter(tag='fatty').delete()
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>>> ctype = ContentType.objects.get_for_model(lion)
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>>> Animal.objects.filter(tags__content_type=ctype)
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[<Animal: Platypus>]
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# Simple tests for multiple GenericForeignKeys
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# only uses one model, since the above tests should be sufficient.
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>>> tiger, cheetah, bear = Animal(common_name="tiger"), Animal(common_name="cheetah"), Animal(common_name="bear")
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>>> for o in [tiger, cheetah, bear]: o.save()
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# Create directly
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>>> Comparison(first_obj=cheetah, other_obj=tiger, comparative="faster").save()
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>>> Comparison(first_obj=tiger, other_obj=cheetah, comparative="cooler").save()
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# Create using GenericRelation
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>>> tiger.comparisons.create(other_obj=bear, comparative="cooler")
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<Comparison: tiger is cooler than bear>
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>>> tiger.comparisons.create(other_obj=cheetah, comparative="stronger")
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<Comparison: tiger is stronger than cheetah>
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>>> cheetah.comparisons.all()
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[<Comparison: cheetah is faster than tiger>]
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# Filtering works
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>>> tiger.comparisons.filter(comparative="cooler")
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[<Comparison: tiger is cooler than cheetah>, <Comparison: tiger is cooler than bear>]
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# Filtering and deleting works
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>>> subjective = ["cooler"]
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>>> tiger.comparisons.filter(comparative__in=subjective).delete()
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>>> Comparison.objects.all()
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[<Comparison: cheetah is faster than tiger>, <Comparison: tiger is stronger than cheetah>]
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# If we delete cheetah, Comparisons with cheetah as 'first_obj' will be deleted
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# since Animal has an explicit GenericRelation to Comparison through first_obj.
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# Comparisons with cheetah as 'other_obj' will not be deleted.
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>>> cheetah.delete()
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>>> Comparison.objects.all()
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[<Comparison: tiger is stronger than None>]
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# GenericForeignKey should work with subclasses (see #8309)
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>>> quartz = Mineral.objects.create(name="Quartz", hardness=7)
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>>> valuedtag = ValuableTaggedItem(content_object=quartz, tag="shiny", value=10)
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>>> valuedtag.save()
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>>> valuedtag.content_object
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<Mineral: Quartz>
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# GenericInlineFormSet tests ##################################################
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>>> from django.contrib.contenttypes.generic import generic_inlineformset_factory
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>>> GenericFormSet = generic_inlineformset_factory(TaggedItem, extra=1)
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>>> formset = GenericFormSet()
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>>> for form in formset.forms:
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... print form.as_p()
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<p><label for="id_generic_relations-taggeditem-content_type-object_id-0-tag">Tag:</label> <input id="id_generic_relations-taggeditem-content_type-object_id-0-tag" type="text" name="generic_relations-taggeditem-content_type-object_id-0-tag" maxlength="50" /></p>
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<p><label for="id_generic_relations-taggeditem-content_type-object_id-0-DELETE">Delete:</label> <input type="checkbox" name="generic_relations-taggeditem-content_type-object_id-0-DELETE" id="id_generic_relations-taggeditem-content_type-object_id-0-DELETE" /><input type="hidden" name="generic_relations-taggeditem-content_type-object_id-0-id" id="id_generic_relations-taggeditem-content_type-object_id-0-id" /></p>
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>>> formset = GenericFormSet(instance=Animal())
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>>> for form in formset.forms:
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... print form.as_p()
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<p><label for="id_generic_relations-taggeditem-content_type-object_id-0-tag">Tag:</label> <input id="id_generic_relations-taggeditem-content_type-object_id-0-tag" type="text" name="generic_relations-taggeditem-content_type-object_id-0-tag" maxlength="50" /></p>
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<p><label for="id_generic_relations-taggeditem-content_type-object_id-0-DELETE">Delete:</label> <input type="checkbox" name="generic_relations-taggeditem-content_type-object_id-0-DELETE" id="id_generic_relations-taggeditem-content_type-object_id-0-DELETE" /><input type="hidden" name="generic_relations-taggeditem-content_type-object_id-0-id" id="id_generic_relations-taggeditem-content_type-object_id-0-id" /></p>
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>>> formset = GenericFormSet(instance=platypus)
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>>> for form in formset.forms:
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... print form.as_p()
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<p><label for="id_generic_relations-taggeditem-content_type-object_id-0-tag">Tag:</label> <input id="id_generic_relations-taggeditem-content_type-object_id-0-tag" type="text" name="generic_relations-taggeditem-content_type-object_id-0-tag" value="shiny" maxlength="50" /></p>
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<p><label for="id_generic_relations-taggeditem-content_type-object_id-0-DELETE">Delete:</label> <input type="checkbox" name="generic_relations-taggeditem-content_type-object_id-0-DELETE" id="id_generic_relations-taggeditem-content_type-object_id-0-DELETE" /><input type="hidden" name="generic_relations-taggeditem-content_type-object_id-0-id" value="..." id="id_generic_relations-taggeditem-content_type-object_id-0-id" /></p>
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<p><label for="id_generic_relations-taggeditem-content_type-object_id-1-tag">Tag:</label> <input id="id_generic_relations-taggeditem-content_type-object_id-1-tag" type="text" name="generic_relations-taggeditem-content_type-object_id-1-tag" maxlength="50" /></p>
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<p><label for="id_generic_relations-taggeditem-content_type-object_id-1-DELETE">Delete:</label> <input type="checkbox" name="generic_relations-taggeditem-content_type-object_id-1-DELETE" id="id_generic_relations-taggeditem-content_type-object_id-1-DELETE" /><input type="hidden" name="generic_relations-taggeditem-content_type-object_id-1-id" id="id_generic_relations-taggeditem-content_type-object_id-1-id" /></p>
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>>> formset = GenericFormSet(instance=lion, prefix='x')
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>>> for form in formset.forms:
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... print form.as_p()
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<p><label for="id_x-0-tag">Tag:</label> <input id="id_x-0-tag" type="text" name="x-0-tag" maxlength="50" /></p>
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<p><label for="id_x-0-DELETE">Delete:</label> <input type="checkbox" name="x-0-DELETE" id="id_x-0-DELETE" /><input type="hidden" name="x-0-id" id="id_x-0-id" /></p>
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"""}
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