+
−import copy
+
−
+
−from django.db.models.query import QuerySet, EmptyQuerySet, insert_query
+
−from django.db.models import signals
+
−from django.db.models.fields import FieldDoesNotExist
+
−
+
−def ensure_default_manager(sender, **kwargs):
+
−    cls = sender
+
−    if not getattr(cls, '_default_manager', None) and not cls._meta.abstract:
+
−        # Create the default manager, if needed.
+
−        try:
+
−            cls._meta.get_field('objects')
+
−            raise ValueError, "Model %s must specify a custom Manager, because it has a field named 'objects'" % cls.__name__
+
−        except FieldDoesNotExist:
+
−            pass
+
−        cls.add_to_class('objects', Manager())
+
−
+
−signals.class_prepared.connect(ensure_default_manager)
+
−
+
−class Manager(object):
+
−    # Tracks each time a Manager instance is created. Used to retain order.
+
−    creation_counter = 0
+
−
+
−    def __init__(self):
+
−        super(Manager, self).__init__()
+
−        self._set_creation_counter()
+
−        self.model = None
+
−        self._inherited = False
+
−
+
−    def contribute_to_class(self, model, name):
+
−        # TODO: Use weakref because of possible memory leak / circular reference.
+
−        self.model = model
+
−        setattr(model, name, ManagerDescriptor(self))
+
−        if not getattr(model, '_default_manager', None) or self.creation_counter < model._default_manager.creation_counter:
+
−            model._default_manager = self
+
−        if model._meta.abstract or self._inherited:
+
−            model._meta.abstract_managers.append((self.creation_counter, name,
+
−                    self))
+
−
+
−    def _set_creation_counter(self):
+
−        """
+
−        Sets the creation counter value for this instance and increments the
+
−        class-level copy.
+
−        """
+
−        self.creation_counter = Manager.creation_counter
+
−        Manager.creation_counter += 1
+
−
+
−    def _copy_to_model(self, model):
+
−        """
+
−        Makes a copy of the manager and assigns it to 'model', which should be
+
−        a child of the existing model (used when inheriting a manager from an
+
−        abstract base class).
+
−        """
+
−        assert issubclass(model, self.model)
+
−        mgr = copy.copy(self)
+
−        mgr._set_creation_counter()
+
−        mgr.model = model
+
−        mgr._inherited = True
+
−        return mgr
+
−
+
−    #######################
+
−    # PROXIES TO QUERYSET #
+
−    #######################
+
−
+
−    def get_empty_query_set(self):
+
−        return EmptyQuerySet(self.model)
+
−
+
−    def get_query_set(self):
+
−        """Returns a new QuerySet object.  Subclasses can override this method
+
−        to easily customize the behavior of the Manager.
+
−        """
+
−        return QuerySet(self.model)
+
−
+
−    def none(self):
+
−        return self.get_empty_query_set()
+
−
+
−    def all(self):
+
−        return self.get_query_set()
+
−
+
−    def count(self):
+
−        return self.get_query_set().count()
+
−
+
−    def dates(self, *args, **kwargs):
+
−        return self.get_query_set().dates(*args, **kwargs)
+
−
+
−    def distinct(self, *args, **kwargs):
+
−        return self.get_query_set().distinct(*args, **kwargs)
+
−
+
−    def extra(self, *args, **kwargs):
+
−        return self.get_query_set().extra(*args, **kwargs)
+
−
+
−    def get(self, *args, **kwargs):
+
−        return self.get_query_set().get(*args, **kwargs)
+
−
+
−    def get_or_create(self, **kwargs):
+
−        return self.get_query_set().get_or_create(**kwargs)
+
−
+
−    def create(self, **kwargs):
+
−        return self.get_query_set().create(**kwargs)
+
−
+
−    def filter(self, *args, **kwargs):
+
−        return self.get_query_set().filter(*args, **kwargs)
+
−
+
−    def complex_filter(self, *args, **kwargs):
+
−        return self.get_query_set().complex_filter(*args, **kwargs)
+
−
+
−    def exclude(self, *args, **kwargs):
+
−        return self.get_query_set().exclude(*args, **kwargs)
+
−
+
−    def in_bulk(self, *args, **kwargs):
+
−        return self.get_query_set().in_bulk(*args, **kwargs)
+
−
+
−    def iterator(self, *args, **kwargs):
+
−        return self.get_query_set().iterator(*args, **kwargs)
+
−
+
−    def latest(self, *args, **kwargs):
+
−        return self.get_query_set().latest(*args, **kwargs)
+
−
+
−    def order_by(self, *args, **kwargs):
+
−        return self.get_query_set().order_by(*args, **kwargs)
+
−
+
−    def select_related(self, *args, **kwargs):
+
−        return self.get_query_set().select_related(*args, **kwargs)
+
−
+
−    def values(self, *args, **kwargs):
+
−        return self.get_query_set().values(*args, **kwargs)
+
−
+
−    def values_list(self, *args, **kwargs):
+
−        return self.get_query_set().values_list(*args, **kwargs)
+
−
+
−    def update(self, *args, **kwargs):
+
−        return self.get_query_set().update(*args, **kwargs)
+
−
+
−    def reverse(self, *args, **kwargs):
+
−        return self.get_query_set().reverse(*args, **kwargs)
+
−
+
−    def _insert(self, values, **kwargs):
+
−        return insert_query(self.model, values, **kwargs)
+
−
+
−    def _update(self, values, **kwargs):
+
−        return self.get_query_set()._update(values, **kwargs)
+
−
+
−class ManagerDescriptor(object):
+
−    # This class ensures managers aren't accessible via model instances.
+
−    # For example, Poll.objects works, but poll_obj.objects raises AttributeError.
+
−    def __init__(self, manager):
+
−        self.manager = manager
+
−
+
−    def __get__(self, instance, type=None):
+
−        if instance != None:
+
−            raise AttributeError, "Manager isn't accessible via %s instances" % type.__name__
+
−        return self.manager
+
−
+
−class EmptyManager(Manager):
+
−    def get_query_set(self):
+
−        return self.get_empty_query_set()