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from django.db import models
from django.utils.translation import ugettext_lazy as _
from django.utils.encoding import smart_unicode, force_unicode
class ContentTypeManager(models.Manager):
# Cache to avoid re-looking up ContentType objects all over the place.
# This cache is shared by all the get_for_* methods.
_cache = {}
def get_by_natural_key(self, app_label, model):
try:
ct = self.__class__._cache[self.db][(app_label, model)]
except KeyError:
ct = self.get(app_label=app_label, model=model)
self._add_to_cache(self.db, ct)
return ct
def _get_opts(self, model):
return model._meta.concrete_model._meta
def _get_from_cache(self, opts):
key = (opts.app_label, opts.object_name.lower())
return self.__class__._cache[self.db][key]
def get_for_model(self, model):
"""
Returns the ContentType object for a given model, creating the
ContentType if necessary. Lookups are cached so that subsequent lookups
for the same model don't hit the database.
"""
opts = self._get_opts(model)
try:
ct = self._get_from_cache(opts)
except KeyError:
# Load or create the ContentType entry. The smart_unicode() is
# needed around opts.verbose_name_raw because name_raw might be a
# django.utils.functional.__proxy__ object.
ct, created = self.get_or_create(
app_label = opts.app_label,
model = opts.object_name.lower(),
defaults = {'name': smart_unicode(opts.verbose_name_raw)},
)
self._add_to_cache(self.db, ct)
return ct
def get_for_models(self, *models):
"""
Given *models, returns a dictionary mapping {model: content_type}.
"""
# Final results
results = {}
# models that aren't already in the cache
needed_app_labels = set()
needed_models = set()
needed_opts = set()
for model in models:
opts = self._get_opts(model)
try:
ct = self._get_from_cache(opts)
except KeyError:
needed_app_labels.add(opts.app_label)
needed_models.add(opts.object_name.lower())
needed_opts.add(opts)
else:
results[model] = ct
if needed_opts:
cts = self.filter(
app_label__in=needed_app_labels,
model__in=needed_models
)
for ct in cts:
model = ct.model_class()
if model._meta in needed_opts:
results[model] = ct
needed_opts.remove(model._meta)
self._add_to_cache(self.db, ct)
for opts in needed_opts:
# These weren't in the cache, or the DB, create them.
ct = self.create(
app_label=opts.app_label,
model=opts.object_name.lower(),
name=smart_unicode(opts.verbose_name_raw),
)
self._add_to_cache(self.db, ct)
results[ct.model_class()] = ct
return results
def get_for_id(self, id):
"""
Lookup a ContentType by ID. Uses the same shared cache as get_for_model
(though ContentTypes are obviously not created on-the-fly by get_by_id).
"""
try:
ct = self.__class__._cache[self.db][id]
except KeyError:
# This could raise a DoesNotExist; that's correct behavior and will
# make sure that only correct ctypes get stored in the cache dict.
ct = self.get(pk=id)
self._add_to_cache(self.db, ct)
return ct
def clear_cache(self):
"""
Clear out the content-type cache. This needs to happen during database
flushes to prevent caching of "stale" content type IDs (see
django.contrib.contenttypes.management.update_contenttypes for where
this gets called).
"""
self.__class__._cache.clear()
def _add_to_cache(self, using, ct):
"""Insert a ContentType into the cache."""
model = ct.model_class()
key = (model._meta.app_label, model._meta.object_name.lower())
self.__class__._cache.setdefault(using, {})[key] = ct
self.__class__._cache.setdefault(using, {})[ct.id] = ct
class ContentType(models.Model):
name = models.CharField(max_length=100)
app_label = models.CharField(max_length=100)
model = models.CharField(_('python model class name'), max_length=100)
objects = ContentTypeManager()
class Meta:
verbose_name = _('content type')
verbose_name_plural = _('content types')
db_table = 'django_content_type'
ordering = ('name',)
unique_together = (('app_label', 'model'),)
def __unicode__(self):
# self.name is deprecated in favor of using model's verbose_name, which
# can be translated. Formal deprecation is delayed until we have DB
# migration to be able to remove the field from the database along with
# the attribute.
#
# We return self.name only when users have changed its value from the
# initial verbose_name_raw and might rely on it.
model = self.model_class()
if not model or self.name != model._meta.verbose_name_raw:
return self.name
else:
return force_unicode(model._meta.verbose_name)
def model_class(self):
"Returns the Python model class for this type of content."
from django.db import models
return models.get_model(self.app_label, self.model,
only_installed=False)
def get_object_for_this_type(self, **kwargs):
"""
Returns an object of this type for the keyword arguments given.
Basically, this is a proxy around this object_type's get_object() model
method. The ObjectNotExist exception, if thrown, will not be caught,
so code that calls this method should catch it.
"""
return self.model_class()._base_manager.using(self._state.db).get(**kwargs)
def get_all_objects_for_this_type(self, **kwargs):
"""
Returns all objects of this type for the keyword arguments given.
"""
return self.model_class()._base_manager.using(self._state.db).filter(**kwargs)
def natural_key(self):
return (self.app_label, self.model)
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