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): """ Ensures that a Model subclass contains a default manager and sets the _default_manager attribute on the class. Also sets up the _base_manager points to a plain Manager instance (which could be the same as _default_manager if it's not a subclass of Manager). """ cls = sender if cls._meta.abstract: return if not getattr(cls, '_default_manager', None): # 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()) cls._base_manager = cls.objects elif not getattr(cls, '_base_manager', None): default_mgr = cls._default_manager.__class__ if (default_mgr is Manager or getattr(default_mgr, "use_for_related_fields", False)): cls._base_manager = cls._default_manager else: # Default manager isn't a plain Manager class, or a suitable # replacement, so we walk up the base class hierarchy until we hit # something appropriate. for base_class in default_mgr.mro()[1:]: if (base_class is Manager or getattr(base_class, "use_for_related_fields", False)): cls.add_to_class('_base_manager', base_class()) return raise AssertionError("Should never get here. Please report a bug, including your model and model manager setup.") 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 and not self.model._meta.proxy): model._meta.abstract_managers.append((self.creation_counter, name, self)) else: model._meta.concrete_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 aggregate(self, *args, **kwargs): return self.get_query_set().aggregate(*args, **kwargs) def annotate(self, *args, **kwargs): return self.get_query_set().annotate(*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 defer(self, *args, **kwargs): return self.get_query_set().defer(*args, **kwargs) def only(self, *args, **kwargs): return self.get_query_set().only(*args, **kwargs) def exists(self, *args, **kwargs): return self.get_query_set().exists(*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()