Models and managers for generic tagging.
"""
-from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.db import connection, models
-from django.utils.translation import ugettext_lazy as _
from django.db.models.base import ModelBase
-from django.core.exceptions import ObjectDoesNotExist
from django.dispatch import Signal
qn = connection.ops.quote_name
# Managers #
############
class TagManager(models.Manager):
- def __init__(self, intermediary_table_model):
+ def __init__(self):
super(TagManager, self).__init__()
- self.intermediary_table_model = intermediary_table_model
models.signals.pre_delete.connect(self.target_deleted)
+ @property
+ def intermediary_table_model(self):
+ return self.model.intermediary_table_model
+
def target_deleted(self, instance, **kwargs):
""" clear tag relations before deleting an object """
try:
content_type = ContentType.objects.get_for_model(obj)
current_tags = list(self.filter(items__content_type__pk=content_type.pk,
items__object_id=obj.pk))
- updated_tags = self.model.get_tag_list(tags)
+ updated_tags = tags
# Remove tags which no longer apply
tags_for_removal = [tag for tag in current_tags if tag not in updated_tags]
object_id=obj.pk,
tag__in=tags_for_removal).delete()
# Add new tags
- tags_to_add = [tag for tag in updated_tags
- if tag not in current_tags]
+ tags_to_add = [tag for tag in updated_tags if tag not in current_tags]
for tag in tags_to_add:
- if tag not in current_tags:
+ existing = self.intermediary_table_model.objects.filter(
+ content_type__pk=content_type.pk, object_id=obj.pk, tag=tag)
+ if not existing:
self.intermediary_table_model.objects.create(tag=tag, content_object=obj)
tags_updated.send(sender=type(obj), instance=obj, affected_tags=tags_to_add + tags_for_removal)
self.intermediary_table_model.objects.filter(
content_type__pk=content_type.pk, object_id=obj.pk, tag=tag).delete()
+ def add_tag(self, obj, tag):
+ """
+ Add tag to an object.
+ """
+ content_type = ContentType.objects.get_for_model(obj)
+ relations = self.intermediary_table_model.objects.filter(
+ content_type__pk=content_type.pk, object_id=obj.pk, tag=tag)
+ if not relations:
+ self.intermediary_table_model.objects.create(tag=tag, content_object=obj)
+
def get_for_object(self, obj):
"""
Create a queryset matching all tags associated with the given
class TaggedItemManager(models.Manager):
- def __init__(self, tag_model):
- super(TaggedItemManager, self).__init__()
- self.tag_model = tag_model
+ @property
+ def tag_model(self):
+ return self.model.tag_model
def get_by_model(self, queryset_or_model, tags):
"""
model associated with a given tag or list of tags.
"""
queryset, model = get_queryset_and_model(queryset_or_model)
- tags = self.tag_model.get_tag_list(tags)
if not tags:
# No existing tags were given
return queryset.none()
model associated with *any* of the given list of tags.
"""
queryset, model = get_queryset_and_model(queryset_or_model)
- tags = self.tag_model.get_tag_list(tags)
if not tags:
return queryset.none()
# TODO: presumes reverse generic relation
# Do we know it's 'tags'?
return queryset.filter(tag_relations__tag__in=obj.tags).annotate(
count=models.Count('pk')).order_by('-count').exclude(pk=obj.pk)
-
-
-##########
-# Models #
-##########
-def create_intermediary_table_model(model):
- """Create an intermediary table model for the specific tag model"""
- name = model.__name__ + 'Relation'
-
- class Meta:
- db_table = '%s_relation' % model._meta.db_table
- unique_together = (('tag', 'content_type', 'object_id'),)
- app_label = model._meta.app_label
-
- def obj_unicode(self):
- try:
- return u'%s [%s]' % (self.content_type.get_object_for_this_type(pk=self.object_id), self.tag)
- except ObjectDoesNotExist:
- return u'<deleted> [%s]' % self.tag
-
- # Set up a dictionary to simulate declarations within a class
- attrs = {
- '__module__': model.__module__,
- 'Meta': Meta,
- 'tag': models.ForeignKey(model, verbose_name=_('tag'), related_name='items'),
- 'content_type': models.ForeignKey(ContentType, verbose_name=_('content type')),
- 'object_id': models.PositiveIntegerField(_('object id'), db_index=True),
- 'content_object': GenericForeignKey('content_type', 'object_id'),
- '__unicode__': obj_unicode,
- }
-
- return type(name, (models.Model,), attrs)
-
-
-class TagMeta(ModelBase):
- """Metaclass for tag models (models inheriting from TagBase)."""
- def __new__(mcs, name, bases, attrs):
- model = super(TagMeta, mcs).__new__(mcs, name, bases, attrs)
- if not model._meta.abstract:
- # Create an intermediary table and register custom managers for concrete models
- model.intermediary_table_model = create_intermediary_table_model(model)
- TagManager(model.intermediary_table_model).contribute_to_class(model, 'objects')
- TaggedItemManager(model).contribute_to_class(model.intermediary_table_model, 'objects')
- return model
-
-
-class TagBase(models.Model):
- """Abstract class to be inherited by model classes."""
- __metaclass__ = TagMeta
-
- class Meta:
- abstract = True
-
- @staticmethod
- def get_tag_list(tag_list):
- """
- Utility function for accepting tag input in a flexible manner.
-
- You should probably override this method in your subclass.
- """
- if isinstance(tag_list, TagBase):
- return [tag_list]
- else:
- return tag_list
fnp / wolnelektury.git / blobdiff