mirror of https://github.com/django/django.git
237 lines
11 KiB
Python
237 lines
11 KiB
Python
"""
|
|
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 django.db import models
|
|
from django.contrib.contenttypes.models import ContentType
|
|
from django.contrib.contenttypes import generic
|
|
|
|
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", "-object_id"]
|
|
|
|
def __unicode__(self):
|
|
return self.tag
|
|
|
|
class ValuableTaggedItem(TaggedItem):
|
|
value = models.PositiveIntegerField()
|
|
|
|
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 __unicode__(self):
|
|
return u"%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 = generic.GenericRelation(TaggedItem)
|
|
comparisons = generic.GenericRelation(Comparison,
|
|
object_id_field="object_id1",
|
|
content_type_field="content_type1")
|
|
|
|
def __unicode__(self):
|
|
return self.common_name
|
|
|
|
class Vegetable(models.Model):
|
|
name = models.CharField(max_length=150)
|
|
is_yucky = models.BooleanField(default=True)
|
|
|
|
tags = generic.GenericRelation(TaggedItem)
|
|
|
|
def __unicode__(self):
|
|
return self.name
|
|
|
|
class Mineral(models.Model):
|
|
name = models.CharField(max_length=150)
|
|
hardness = models.PositiveSmallIntegerField()
|
|
|
|
# note the lack of an explicit GenericRelation here...
|
|
|
|
def __unicode__(self):
|
|
return self.name
|
|
|
|
__test__ = {'API_TESTS':"""
|
|
# Create the world in 7 lines of code...
|
|
>>> lion = Animal(common_name="Lion", latin_name="Panthera leo")
|
|
>>> platypus = Animal(common_name="Platypus", latin_name="Ornithorhynchus anatinus")
|
|
>>> eggplant = Vegetable(name="Eggplant", is_yucky=True)
|
|
>>> bacon = Vegetable(name="Bacon", is_yucky=False)
|
|
>>> quartz = Mineral(name="Quartz", hardness=7)
|
|
>>> for o in (platypus, lion, eggplant, bacon, quartz):
|
|
... o.save()
|
|
|
|
# Objects with declared GenericRelations can be tagged directly -- the API
|
|
# mimics the many-to-many API.
|
|
>>> bacon.tags.create(tag="fatty")
|
|
<TaggedItem: fatty>
|
|
>>> bacon.tags.create(tag="salty")
|
|
<TaggedItem: salty>
|
|
>>> lion.tags.create(tag="yellow")
|
|
<TaggedItem: yellow>
|
|
>>> lion.tags.create(tag="hairy")
|
|
<TaggedItem: hairy>
|
|
>>> platypus.tags.create(tag="fatty")
|
|
<TaggedItem: fatty>
|
|
|
|
>>> lion.tags.all()
|
|
[<TaggedItem: hairy>, <TaggedItem: yellow>]
|
|
>>> bacon.tags.all()
|
|
[<TaggedItem: fatty>, <TaggedItem: salty>]
|
|
|
|
# You can easily access the content object like a foreign key.
|
|
>>> t = TaggedItem.objects.get(tag="salty")
|
|
>>> t.content_object
|
|
<Vegetable: Bacon>
|
|
|
|
# Recall that the Mineral class doesn't have an explicit GenericRelation
|
|
# defined. That's OK, because you can create TaggedItems explicitly.
|
|
>>> tag1 = TaggedItem(content_object=quartz, tag="shiny")
|
|
>>> tag2 = TaggedItem(content_object=quartz, tag="clearish")
|
|
>>> tag1.save()
|
|
>>> tag2.save()
|
|
|
|
# However, excluding GenericRelations means your lookups have to be a bit more
|
|
# explicit.
|
|
>>> from django.contrib.contenttypes.models import ContentType
|
|
>>> ctype = ContentType.objects.get_for_model(quartz)
|
|
>>> TaggedItem.objects.filter(content_type__pk=ctype.id, object_id=quartz.id)
|
|
[<TaggedItem: clearish>, <TaggedItem: shiny>]
|
|
|
|
# You can set a generic foreign key in the way you'd expect.
|
|
>>> tag1.content_object = platypus
|
|
>>> tag1.save()
|
|
>>> platypus.tags.all()
|
|
[<TaggedItem: fatty>, <TaggedItem: shiny>]
|
|
>>> TaggedItem.objects.filter(content_type__pk=ctype.id, object_id=quartz.id)
|
|
[<TaggedItem: clearish>]
|
|
|
|
# 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.
|
|
>>> Animal.objects.order_by('common_name')
|
|
[<Animal: Lion>, <Animal: Platypus>]
|
|
>>> Animal.objects.filter(tags__tag='fatty')
|
|
[<Animal: Platypus>]
|
|
>>> Animal.objects.exclude(tags__tag='fatty')
|
|
[<Animal: Lion>]
|
|
|
|
# If you delete an object with an explicit Generic relation, the related
|
|
# objects are deleted when the source object is deleted.
|
|
# Original list of tags:
|
|
>>> [(t.tag, t.content_type, t.object_id) for t in TaggedItem.objects.all()]
|
|
[(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)]
|
|
|
|
>>> lion.delete()
|
|
>>> [(t.tag, t.content_type, t.object_id) for t in TaggedItem.objects.all()]
|
|
[(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)]
|
|
|
|
# If Generic Relation is not explicitly defined, any related objects
|
|
# remain after deletion of the source object.
|
|
>>> quartz.delete()
|
|
>>> [(t.tag, t.content_type, t.object_id) for t in TaggedItem.objects.all()]
|
|
[(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)]
|
|
|
|
# If you delete a tag, the objects using the tag are unaffected
|
|
# (other than losing a tag)
|
|
>>> tag = TaggedItem.objects.get(id=1)
|
|
>>> tag.delete()
|
|
>>> bacon.tags.all()
|
|
[<TaggedItem: salty>]
|
|
>>> [(t.tag, t.content_type, t.object_id) for t in TaggedItem.objects.all()]
|
|
[(u'clearish', <ContentType: mineral>, 1), (u'fatty', <ContentType: animal>, 1), (u'salty', <ContentType: vegetable>, 2), (u'shiny', <ContentType: animal>, 1)]
|
|
|
|
>>> TaggedItem.objects.filter(tag='fatty').delete()
|
|
|
|
>>> ctype = ContentType.objects.get_for_model(lion)
|
|
>>> Animal.objects.filter(tags__content_type=ctype)
|
|
[<Animal: Platypus>]
|
|
|
|
# Simple tests for multiple GenericForeignKeys
|
|
# only uses one model, since the above tests should be sufficient.
|
|
>>> tiger, cheetah, bear = Animal(common_name="tiger"), Animal(common_name="cheetah"), Animal(common_name="bear")
|
|
>>> for o in [tiger, cheetah, bear]: o.save()
|
|
|
|
# Create directly
|
|
>>> Comparison(first_obj=cheetah, other_obj=tiger, comparative="faster").save()
|
|
>>> Comparison(first_obj=tiger, other_obj=cheetah, comparative="cooler").save()
|
|
|
|
# Create using GenericRelation
|
|
>>> tiger.comparisons.create(other_obj=bear, comparative="cooler")
|
|
<Comparison: tiger is cooler than bear>
|
|
>>> tiger.comparisons.create(other_obj=cheetah, comparative="stronger")
|
|
<Comparison: tiger is stronger than cheetah>
|
|
|
|
>>> cheetah.comparisons.all()
|
|
[<Comparison: cheetah is faster than tiger>]
|
|
|
|
# Filtering works
|
|
>>> tiger.comparisons.filter(comparative="cooler")
|
|
[<Comparison: tiger is cooler than cheetah>, <Comparison: tiger is cooler than bear>]
|
|
|
|
# Filtering and deleting works
|
|
>>> subjective = ["cooler"]
|
|
>>> tiger.comparisons.filter(comparative__in=subjective).delete()
|
|
>>> Comparison.objects.all()
|
|
[<Comparison: cheetah is faster than tiger>, <Comparison: tiger is stronger than cheetah>]
|
|
|
|
# If we delete cheetah, Comparisons with cheetah as 'first_obj' will be deleted
|
|
# since Animal has an explicit GenericRelation to Comparison through first_obj.
|
|
# Comparisons with cheetah as 'other_obj' will not be deleted.
|
|
>>> cheetah.delete()
|
|
>>> Comparison.objects.all()
|
|
[<Comparison: tiger is stronger than None>]
|
|
|
|
# GenericForeignKey should work with subclasses (see #8309)
|
|
>>> quartz = Mineral.objects.create(name="Quartz", hardness=7)
|
|
>>> valuedtag = ValuableTaggedItem(content_object=quartz, tag="shiny", value=10)
|
|
>>> valuedtag.save()
|
|
>>> valuedtag.content_object
|
|
<Mineral: Quartz>
|
|
|
|
# GenericInlineFormSet tests ##################################################
|
|
|
|
>>> from django.contrib.contenttypes.generic import generic_inlineformset_factory
|
|
|
|
>>> GenericFormSet = generic_inlineformset_factory(TaggedItem, extra=1)
|
|
>>> formset = GenericFormSet(instance=Animal())
|
|
>>> for form in formset.forms:
|
|
... print form.as_p()
|
|
<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>
|
|
<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>
|
|
|
|
>>> formset = GenericFormSet(instance=platypus)
|
|
>>> for form in formset.forms:
|
|
... print form.as_p()
|
|
<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>
|
|
<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>
|
|
<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>
|
|
<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>
|
|
|
|
"""}
|