Source code for django.contrib.contenttypes.fields
from __future__ import unicode_literals
from collections import defaultdict
from django.contrib.contenttypes.models import ContentType
from django.core import checks
from django.core.exceptions import FieldDoesNotExist, ObjectDoesNotExist
from django.db import DEFAULT_DB_ALIAS, connection, models, router, transaction
from django.db.models import DO_NOTHING, signals
from django.db.models.base import ModelBase
from django.db.models.fields.related import ForeignObject, ForeignObjectRel
from django.db.models.query_utils import PathInfo
from django.utils.encoding import python_2_unicode_compatible, smart_text
[docs]@python_2_unicode_compatible
class GenericForeignKey(object):
"""
Provides a generic relation to any object through content-type/object-id
fields.
"""
# Field flags
auto_created = False
concrete = False
editable = False
hidden = False
is_relation = True
many_to_many = False
many_to_one = True
one_to_many = False
one_to_one = False
related_model = None
# For backwards compatibility; ignored as of Django 1.8.4.
allow_unsaved_instance_assignment = False
def __init__(self, ct_field="content_type", fk_field="object_id", for_concrete_model=True):
self.ct_field = ct_field
self.fk_field = fk_field
self.for_concrete_model = for_concrete_model
self.editable = False
self.rel = None
self.column = None
def contribute_to_class(self, cls, name, **kwargs):
self.name = name
self.model = cls
self.cache_attr = "_%s_cache" % name
cls._meta.add_field(self, virtual=True)
# Only run pre-initialization field assignment on non-abstract models
if not cls._meta.abstract:
signals.pre_init.connect(self.instance_pre_init, sender=cls)
setattr(cls, name, self)
def __str__(self):
model = self.model
app = model._meta.app_label
return '%s.%s.%s' % (app, model._meta.object_name, self.name)
def check(self, **kwargs):
errors = []
errors.extend(self._check_field_name())
errors.extend(self._check_object_id_field())
errors.extend(self._check_content_type_field())
return errors
def _check_field_name(self):
if self.name.endswith("_"):
return [
checks.Error(
'Field names must not end with an underscore.',
hint=None,
obj=self,
id='fields.E001',
)
]
else:
return []
def _check_object_id_field(self):
try:
self.model._meta.get_field(self.fk_field)
except FieldDoesNotExist:
return [
checks.Error(
"The GenericForeignKey object ID references the non-existent field '%s'." % self.fk_field,
hint=None,
obj=self,
id='contenttypes.E001',
)
]
else:
return []
def _check_content_type_field(self):
""" Check if field named `field_name` in model `model` exists and is
valid content_type field (is a ForeignKey to ContentType). """
try:
field = self.model._meta.get_field(self.ct_field)
except FieldDoesNotExist:
return [
checks.Error(
"The GenericForeignKey content type references the non-existent field '%s.%s'." % (
self.model._meta.object_name, self.ct_field
),
hint=None,
obj=self,
id='contenttypes.E002',
)
]
else:
if not isinstance(field, models.ForeignKey):
return [
checks.Error(
"'%s.%s' is not a ForeignKey." % (
self.model._meta.object_name, self.ct_field
),
hint=(
"GenericForeignKeys must use a ForeignKey to "
"'contenttypes.ContentType' as the 'content_type' field."
),
obj=self,
id='contenttypes.E003',
)
]
elif field.rel.to != ContentType:
return [
checks.Error(
"'%s.%s' is not a ForeignKey to 'contenttypes.ContentType'." % (
self.model._meta.object_name, self.ct_field
),
hint=(
"GenericForeignKeys must use a ForeignKey to "
"'contenttypes.ContentType' as the 'content_type' field."
),
obj=self,
id='contenttypes.E004',
)
]
else:
return []
def instance_pre_init(self, signal, sender, args, kwargs, **_kwargs):
"""
Handles initializing an object with the generic FK instead of
content-type/object-id fields.
"""
if self.name in kwargs:
value = kwargs.pop(self.name)
if value is not None:
kwargs[self.ct_field] = self.get_content_type(obj=value)
kwargs[self.fk_field] = value._get_pk_val()
else:
kwargs[self.ct_field] = None
kwargs[self.fk_field] = None
def get_content_type(self, obj=None, id=None, using=None):
if obj is not None:
return ContentType.objects.db_manager(obj._state.db).get_for_model(
obj, for_concrete_model=self.for_concrete_model)
elif id is not None:
return ContentType.objects.db_manager(using).get_for_id(id)
else:
# This should never happen. I love comments like this, don't you?
raise Exception("Impossible arguments to GFK.get_content_type!")
def get_prefetch_queryset(self, instances, queryset=None):
if queryset is not None:
raise ValueError("Custom queryset can't be used for this lookup.")
# For efficiency, group the instances by content type and then do one
# query per model
fk_dict = defaultdict(set)
# We need one instance for each group in order to get the right db:
instance_dict = {}
ct_attname = self.model._meta.get_field(self.ct_field).get_attname()
for instance in instances:
# We avoid looking for values if either ct_id or fkey value is None
ct_id = getattr(instance, ct_attname)
if ct_id is not None:
fk_val = getattr(instance, self.fk_field)
if fk_val is not None:
fk_dict[ct_id].add(fk_val)
instance_dict[ct_id] = instance
ret_val = []
for ct_id, fkeys in fk_dict.items():
instance = instance_dict[ct_id]
ct = self.get_content_type(id=ct_id, using=instance._state.db)
ret_val.extend(ct.get_all_objects_for_this_type(pk__in=fkeys))
# For doing the join in Python, we have to match both the FK val and the
# content type, so we use a callable that returns a (fk, class) pair.
def gfk_key(obj):
ct_id = getattr(obj, ct_attname)
if ct_id is None:
return None
else:
model = self.get_content_type(id=ct_id,
using=obj._state.db).model_class()
return (model._meta.pk.get_prep_value(getattr(obj, self.fk_field)),
model)
return (ret_val,
lambda obj: (obj._get_pk_val(), obj.__class__),
gfk_key,
True,
self.cache_attr)
def is_cached(self, instance):
return hasattr(instance, self.cache_attr)
def __get__(self, instance, instance_type=None):
if instance is None:
return self
try:
return getattr(instance, self.cache_attr)
except AttributeError:
rel_obj = None
# Make sure to use ContentType.objects.get_for_id() to ensure that
# lookups are cached (see ticket #5570). This takes more code than
# the naive ``getattr(instance, self.ct_field)``, but has better
# performance when dealing with GFKs in loops and such.
f = self.model._meta.get_field(self.ct_field)
ct_id = getattr(instance, f.get_attname(), None)
if ct_id is not None:
ct = self.get_content_type(id=ct_id, using=instance._state.db)
try:
rel_obj = ct.get_object_for_this_type(pk=getattr(instance, self.fk_field))
except ObjectDoesNotExist:
pass
setattr(instance, self.cache_attr, rel_obj)
return rel_obj
def __set__(self, instance, value):
ct = None
fk = None
if value is not None:
ct = self.get_content_type(obj=value)
fk = value._get_pk_val()
setattr(instance, self.ct_field, ct)
setattr(instance, self.fk_field, fk)
setattr(instance, self.cache_attr, value)
[docs]class GenericRelation(ForeignObject):
"""Provides an accessor to generic related objects (e.g. comments)"""
# Field flags
auto_created = False
many_to_many = False
many_to_one = False
one_to_many = True
one_to_one = False
def __init__(self, to, **kwargs):
kwargs['verbose_name'] = kwargs.get('verbose_name', None)
kwargs['rel'] = GenericRel(
self, to,
related_query_name=kwargs.pop('related_query_name', None),
limit_choices_to=kwargs.pop('limit_choices_to', None),
)
# Override content-type/object-id field names on the related class
self.object_id_field_name = kwargs.pop("object_id_field", "object_id")
self.content_type_field_name = kwargs.pop("content_type_field", "content_type")
self.for_concrete_model = kwargs.pop("for_concrete_model", True)
kwargs['blank'] = True
kwargs['editable'] = False
kwargs['serialize'] = False
# This construct is somewhat of an abuse of ForeignObject. This field
# represents a relation from pk to object_id field. But, this relation
# isn't direct, the join is generated reverse along foreign key. So,
# the from_field is object_id field, to_field is pk because of the
# reverse join.
super(GenericRelation, self).__init__(
to, to_fields=[],
from_fields=[self.object_id_field_name], **kwargs)
def check(self, **kwargs):
errors = super(GenericRelation, self).check(**kwargs)
errors.extend(self._check_generic_foreign_key_existence())
return errors
def _check_generic_foreign_key_existence(self):
target = self.rel.to
if isinstance(target, ModelBase):
# Using `vars` is very ugly approach, but there is no better one,
# because GenericForeignKeys are not considered as fields and,
# therefore, are not included in `target._meta.local_fields`.
fields = target._meta.virtual_fields
if any(isinstance(field, GenericForeignKey) and
field.ct_field == self.content_type_field_name and
field.fk_field == self.object_id_field_name
for field in fields):
return []
else:
return [
checks.Error(
("The GenericRelation defines a relation with the model "
"'%s.%s', but that model does not have a GenericForeignKey.") % (
target._meta.app_label, target._meta.object_name
),
hint=None,
obj=self,
id='contenttypes.E004',
)
]
else:
return []
def resolve_related_fields(self):
self.to_fields = [self.model._meta.pk.name]
return [(self.rel.to._meta.get_field(self.object_id_field_name), self.model._meta.pk)]
def get_path_info(self):
opts = self.rel.to._meta
target = opts.pk
return [PathInfo(self.model._meta, opts, (target,), self.rel, True, False)]
def get_reverse_path_info(self):
opts = self.model._meta
from_opts = self.rel.to._meta
return [PathInfo(from_opts, opts, (opts.pk,), self, not self.unique, False)]
def get_choices_default(self):
return super(GenericRelation, self).get_choices(include_blank=False)
def value_to_string(self, obj):
qs = getattr(obj, self.name).all()
return smart_text([instance._get_pk_val() for instance in qs])
def contribute_to_class(self, cls, name, **kwargs):
kwargs['virtual_only'] = True
super(GenericRelation, self).contribute_to_class(cls, name, **kwargs)
# Save a reference to which model this class is on for future use
self.model = cls
# Add the descriptor for the relation
setattr(cls, self.name, ReverseGenericRelatedObjectsDescriptor(self, self.for_concrete_model))
def set_attributes_from_rel(self):
pass
def get_internal_type(self):
return "ManyToManyField"
def get_content_type(self):
"""
Returns the content type associated with this field's model.
"""
return ContentType.objects.get_for_model(self.model,
for_concrete_model=self.for_concrete_model)
def get_extra_restriction(self, where_class, alias, remote_alias):
field = self.rel.to._meta.get_field(self.content_type_field_name)
contenttype_pk = self.get_content_type().pk
cond = where_class()
lookup = field.get_lookup('exact')(field.get_col(remote_alias), contenttype_pk)
cond.add(lookup, 'AND')
return cond
def bulk_related_objects(self, objs, using=DEFAULT_DB_ALIAS):
"""
Return all objects related to ``objs`` via this ``GenericRelation``.
"""
return self.rel.to._base_manager.db_manager(using).filter(**{
"%s__pk" % self.content_type_field_name: ContentType.objects.db_manager(using).get_for_model(
self.model, for_concrete_model=self.for_concrete_model).pk,
"%s__in" % self.object_id_field_name: [obj.pk for obj in objs]
})
class ReverseGenericRelatedObjectsDescriptor(object):
"""
This class provides the functionality that makes the related-object
managers available as attributes on a model class, for fields that have
multiple "remote" values and have a GenericRelation defined in their model
(rather than having another model pointed *at* them). In the example
"article.publications", the publications attribute is a
ReverseGenericRelatedObjectsDescriptor instance.
"""
def __init__(self, field, for_concrete_model=True):
self.field = field
self.for_concrete_model = for_concrete_model
def __get__(self, instance, instance_type=None):
if instance is None:
return self
# Dynamically create a class that subclasses the related model's
# default manager.
rel_model = self.field.rel.to
superclass = rel_model._default_manager.__class__
RelatedManager = create_generic_related_manager(superclass)
qn = connection.ops.quote_name
content_type = ContentType.objects.db_manager(instance._state.db).get_for_model(
instance, for_concrete_model=self.for_concrete_model)
join_cols = self.field.get_joining_columns(reverse_join=True)[0]
manager = RelatedManager(
model=rel_model,
instance=instance,
source_col_name=qn(join_cols[0]),
target_col_name=qn(join_cols[1]),
content_type=content_type,
content_type_field_name=self.field.content_type_field_name,
object_id_field_name=self.field.object_id_field_name,
prefetch_cache_name=self.field.attname,
)
return manager
def __set__(self, instance, value):
# Force evaluation of `value` in case it's a queryset whose
# value could be affected by `manager.clear()`. Refs #19816.
value = tuple(value)
manager = self.__get__(instance)
db = router.db_for_write(manager.model, instance=manager.instance)
with transaction.atomic(using=db, savepoint=False):
manager.clear()
for obj in value:
manager.add(obj)
def create_generic_related_manager(superclass):
"""
Factory function for a manager that subclasses 'superclass' (which is a
Manager) and adds behavior for generic related objects.
"""
class GenericRelatedObjectManager(superclass):
def __init__(self, model=None, instance=None, symmetrical=None,
source_col_name=None, target_col_name=None, content_type=None,
content_type_field_name=None, object_id_field_name=None,
prefetch_cache_name=None):
super(GenericRelatedObjectManager, self).__init__()
self.model = model
self.content_type = content_type
self.symmetrical = symmetrical
self.instance = instance
self.source_col_name = source_col_name
self.target_col_name = target_col_name
self.content_type_field_name = content_type_field_name
self.object_id_field_name = object_id_field_name
self.prefetch_cache_name = prefetch_cache_name
self.pk_val = self.instance._get_pk_val()
self.core_filters = {
'%s__pk' % content_type_field_name: content_type.id,
'%s' % object_id_field_name: instance._get_pk_val(),
}
def __call__(self, **kwargs):
# We use **kwargs rather than a kwarg argument to enforce the
# `manager='manager_name'` syntax.
manager = getattr(self.model, kwargs.pop('manager'))
manager_class = create_generic_related_manager(manager.__class__)
return manager_class(
model=self.model,
instance=self.instance,
symmetrical=self.symmetrical,
source_col_name=self.source_col_name,
target_col_name=self.target_col_name,
content_type=self.content_type,
content_type_field_name=self.content_type_field_name,
object_id_field_name=self.object_id_field_name,
prefetch_cache_name=self.prefetch_cache_name,
)
do_not_call_in_templates = True
def __str__(self):
return repr(self)
def get_queryset(self):
try:
return self.instance._prefetched_objects_cache[self.prefetch_cache_name]
except (AttributeError, KeyError):
db = self._db or router.db_for_read(self.model, instance=self.instance)
return super(GenericRelatedObjectManager, self).get_queryset().using(db).filter(**self.core_filters)
def get_prefetch_queryset(self, instances, queryset=None):
if queryset is None:
queryset = super(GenericRelatedObjectManager, self).get_queryset()
queryset._add_hints(instance=instances[0])
queryset = queryset.using(queryset._db or self._db)
query = {
'%s__pk' % self.content_type_field_name: self.content_type.id,
'%s__in' % self.object_id_field_name: set(obj._get_pk_val() for obj in instances)
}
# We (possibly) need to convert object IDs to the type of the
# instances' PK in order to match up instances:
object_id_converter = instances[0]._meta.pk.to_python
return (queryset.filter(**query),
lambda relobj: object_id_converter(getattr(relobj, self.object_id_field_name)),
lambda obj: obj._get_pk_val(),
False,
self.prefetch_cache_name)
def add(self, *objs):
db = router.db_for_write(self.model, instance=self.instance)
with transaction.atomic(using=db, savepoint=False):
for obj in objs:
if not isinstance(obj, self.model):
raise TypeError("'%s' instance expected" % self.model._meta.object_name)
setattr(obj, self.content_type_field_name, self.content_type)
setattr(obj, self.object_id_field_name, self.pk_val)
obj.save()
add.alters_data = True
def remove(self, *objs, **kwargs):
if not objs:
return
bulk = kwargs.pop('bulk', True)
self._clear(self.filter(pk__in=[o.pk for o in objs]), bulk)
remove.alters_data = True
def clear(self, **kwargs):
bulk = kwargs.pop('bulk', True)
self._clear(self, bulk)
clear.alters_data = True
def _clear(self, queryset, bulk):
db = router.db_for_write(self.model, instance=self.instance)
queryset = queryset.using(db)
if bulk:
# `QuerySet.delete()` creates its own atomic block which
# contains the `pre_delete` and `post_delete` signal handlers.
queryset.delete()
else:
with transaction.atomic(using=db, savepoint=False):
for obj in queryset:
obj.delete()
_clear.alters_data = True
def create(self, **kwargs):
kwargs[self.content_type_field_name] = self.content_type
kwargs[self.object_id_field_name] = self.pk_val
db = router.db_for_write(self.model, instance=self.instance)
return super(GenericRelatedObjectManager, self).using(db).create(**kwargs)
create.alters_data = True
def get_or_create(self, **kwargs):
kwargs[self.content_type_field_name] = self.content_type
kwargs[self.object_id_field_name] = self.pk_val
db = router.db_for_write(self.model, instance=self.instance)
return super(GenericRelatedObjectManager, self).using(db).get_or_create(**kwargs)
get_or_create.alters_data = True
def update_or_create(self, **kwargs):
kwargs[self.content_type_field_name] = self.content_type
kwargs[self.object_id_field_name] = self.pk_val
db = router.db_for_write(self.model, instance=self.instance)
return super(GenericRelatedObjectManager, self).using(db).update_or_create(**kwargs)
update_or_create.alters_data = True
return GenericRelatedObjectManager
class GenericRel(ForeignObjectRel):
def __init__(self, field, to, related_name=None, limit_choices_to=None, related_query_name=None):
super(GenericRel, self).__init__(field=field, to=to, related_name=related_query_name or '+',
limit_choices_to=limit_choices_to, on_delete=DO_NOTHING,
related_query_name=related_query_name)
