--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/app/django/contrib/contenttypes/generic.py Fri Jul 18 18:22:23 2008 +0000
@@ -0,0 +1,283 @@
+"""
+Classes allowing "generic" relations through ContentType and object-id fields.
+"""
+
+from django import oldforms
+from django.core.exceptions import ObjectDoesNotExist
+from django.db import connection
+from django.db.models import signals
+from django.db.models.fields.related import RelatedField, Field, ManyToManyRel
+from django.db.models.loading import get_model
+from django.dispatch import dispatcher
+from django.utils.functional import curry
+
+class GenericForeignKey(object):
+ """
+ Provides a generic relation to any object through content-type/object-id
+ fields.
+ """
+
+ def __init__(self, ct_field="content_type", fk_field="object_id"):
+ self.ct_field = ct_field
+ self.fk_field = fk_field
+
+ def contribute_to_class(self, cls, name):
+ # Make sure the fields exist (these raise FieldDoesNotExist,
+ # which is a fine error to raise here)
+ self.name = name
+ self.model = cls
+ self.cache_attr = "_%s_cache" % name
+
+ # For some reason I don't totally understand, using weakrefs here doesn't work.
+ dispatcher.connect(self.instance_pre_init, signal=signals.pre_init, sender=cls, weak=False)
+
+ # Connect myself as the descriptor for this field
+ setattr(cls, name, self)
+
+ def instance_pre_init(self, signal, sender, args, kwargs):
+ """
+ Handles initializing an object with the generic FK instaed of
+ content-type/object-id fields.
+ """
+ if self.name in kwargs:
+ value = kwargs.pop(self.name)
+ kwargs[self.ct_field] = self.get_content_type(obj=value)
+ kwargs[self.fk_field] = value._get_pk_val()
+
+ def get_content_type(self, obj=None, id=None):
+ # Convenience function using get_model avoids a circular import when
+ # using this model
+ ContentType = get_model("contenttypes", "contenttype")
+ if obj:
+ return ContentType.objects.get_for_model(obj)
+ elif id:
+ return ContentType.objects.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__(self, instance, instance_type=None):
+ if instance is None:
+ raise AttributeError, u"%s must be accessed via instance" % self.name
+
+ 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:
+ ct = self.get_content_type(id=ct_id)
+ 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):
+ if instance is None:
+ raise AttributeError, u"%s must be accessed via instance" % self.related.opts.object_name
+
+ 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)
+
+class GenericRelation(RelatedField, Field):
+ """Provides an accessor to generic related objects (i.e. comments)"""
+
+ def __init__(self, to, **kwargs):
+ kwargs['verbose_name'] = kwargs.get('verbose_name', None)
+ kwargs['rel'] = GenericRel(to,
+ related_name=kwargs.pop('related_name', None),
+ limit_choices_to=kwargs.pop('limit_choices_to', None),
+ symmetrical=kwargs.pop('symmetrical', True))
+
+ # 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")
+
+ kwargs['blank'] = True
+ kwargs['editable'] = False
+ kwargs['serialize'] = False
+ Field.__init__(self, **kwargs)
+
+ def get_manipulator_field_objs(self):
+ choices = self.get_choices_default()
+ return [curry(oldforms.SelectMultipleField, size=min(max(len(choices), 5), 15), choices=choices)]
+
+ def get_choices_default(self):
+ return Field.get_choices(self, include_blank=False)
+
+ def flatten_data(self, follow, obj = None):
+ new_data = {}
+ if obj:
+ instance_ids = [instance._get_pk_val() for instance in getattr(obj, self.name).all()]
+ new_data[self.name] = instance_ids
+ return new_data
+
+ def m2m_db_table(self):
+ return self.rel.to._meta.db_table
+
+ def m2m_column_name(self):
+ return self.object_id_field_name
+
+ def m2m_reverse_name(self):
+ return self.model._meta.pk.column
+
+ def contribute_to_class(self, cls, name):
+ super(GenericRelation, self).contribute_to_class(cls, name)
+
+ # Save a reference to which model this class is on for future use
+ self.model = cls
+
+ # Add the descriptor for the m2m relation
+ setattr(cls, self.name, ReverseGenericRelatedObjectsDescriptor(self))
+
+ def contribute_to_related_class(self, cls, related):
+ pass
+
+ def set_attributes_from_rel(self):
+ pass
+
+ def get_internal_type(self):
+ return "ManyToManyField"
+
+ def db_type(self):
+ # Since we're simulating a ManyToManyField, in effect, best return the
+ # same db_type as well.
+ return None
+
+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):
+ self.field = field
+
+ def __get__(self, instance, instance_type=None):
+ if instance is None:
+ raise AttributeError, "Manager must be accessed via instance"
+
+ # This import is done here to avoid circular import importing this module
+ from django.contrib.contenttypes.models import ContentType
+
+ # 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
+
+ manager = RelatedManager(
+ model = rel_model,
+ instance = instance,
+ symmetrical = (self.field.rel.symmetrical and instance.__class__ == rel_model),
+ join_table = qn(self.field.m2m_db_table()),
+ source_col_name = qn(self.field.m2m_column_name()),
+ target_col_name = qn(self.field.m2m_reverse_name()),
+ content_type = ContentType.objects.get_for_model(self.field.model),
+ content_type_field_name = self.field.content_type_field_name,
+ object_id_field_name = self.field.object_id_field_name
+ )
+
+ return manager
+
+ def __set__(self, instance, value):
+ if instance is None:
+ raise AttributeError, "Manager must be accessed via instance"
+
+ manager = self.__get__(instance)
+ 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, core_filters=None, instance=None, symmetrical=None,
+ join_table=None, source_col_name=None, target_col_name=None, content_type=None,
+ content_type_field_name=None, object_id_field_name=None):
+
+ super(GenericRelatedObjectManager, self).__init__()
+ self.core_filters = core_filters or {}
+ self.model = model
+ self.content_type = content_type
+ self.symmetrical = symmetrical
+ self.instance = instance
+ self.join_table = join_table
+ self.join_table = model._meta.db_table
+ 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.pk_val = self.instance._get_pk_val()
+
+ def get_query_set(self):
+ query = {
+ '%s__pk' % self.content_type_field_name : self.content_type.id,
+ '%s__exact' % self.object_id_field_name : self.pk_val,
+ }
+ return superclass.get_query_set(self).filter(**query)
+
+ def add(self, *objs):
+ for obj in objs:
+ 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):
+ for obj in objs:
+ obj.delete()
+ remove.alters_data = True
+
+ def clear(self):
+ for obj in self.all():
+ 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
+ obj = self.model(**kwargs)
+ obj.save()
+ return obj
+ create.alters_data = True
+
+ return GenericRelatedObjectManager
+
+class GenericRel(ManyToManyRel):
+ def __init__(self, to, related_name=None, limit_choices_to=None, symmetrical=True):
+ self.to = to
+ self.num_in_admin = 0
+ self.related_name = related_name
+ self.filter_interface = None
+ self.limit_choices_to = limit_choices_to or {}
+ self.edit_inline = False
+ self.raw_id_admin = False
+ self.symmetrical = symmetrical
+ self.multiple = True
+ assert not (self.raw_id_admin and self.filter_interface), \
+ "Generic relations may not use both raw_id_admin and filter_interface"