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|
# attributes.py - manages object attributes
# Copyright (C) 2005, 2006, 2007 Michael Bayer mike_mp@zzzcomputing.com
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
import weakref, threading
import UserDict
from sqlalchemy import util
from sqlalchemy.orm import interfaces, collections
from sqlalchemy.orm.mapper import class_mapper, identity_equal
from sqlalchemy import exceptions
PASSIVE_NORESULT = object()
ATTR_WAS_SET = object()
NO_VALUE = object()
class InstrumentedAttribute(interfaces.PropComparator):
"""public-facing instrumented attribute."""
def __init__(self, impl, comparator=None):
"""Construct an InstrumentedAttribute.
comparator
a sql.Comparator to which class-level compare/math events will be sent
"""
self.impl = impl
self.comparator = comparator
def __set__(self, obj, value):
self.impl.set(obj._state, value, None)
def __delete__(self, obj):
self.impl.delete(obj._state)
def __get__(self, obj, owner):
if obj is None:
return self
return self.impl.get(obj._state)
def get_history(self, obj, **kwargs):
return self.impl.get_history(obj._state, **kwargs)
def clause_element(self):
return self.comparator.clause_element()
def expression_element(self):
return self.comparator.expression_element()
def operate(self, op, *other, **kwargs):
return op(self.comparator, *other, **kwargs)
def reverse_operate(self, op, other, **kwargs):
return op(other, self.comparator, **kwargs)
def hasparent(self, instance, optimistic=False):
return self.impl.hasparent(instance._state, optimistic=optimistic)
property = property(lambda s: class_mapper(s.impl.class_).get_property(s.impl.key),
doc="the MapperProperty object associated with this attribute")
class AttributeImpl(object):
"""internal implementation for instrumented attributes."""
def __init__(self, class_, manager, key, callable_, trackparent=False, extension=None, compare_function=None, mutable_scalars=False, **kwargs):
"""Construct an AttributeImpl.
class_
the class to be instrumented.
manager
AttributeManager managing this class
key
string name of the attribute
callable_
optional function which generates a callable based on a parent
instance, which produces the "default" values for a scalar or
collection attribute when it's first accessed, if not present already.
trackparent
if True, attempt to track if an instance has a parent attached to it
via this attribute
extension
an AttributeExtension object which will receive
set/delete/append/remove/etc. events
compare_function
a function that compares two values which are normally assignable to this
attribute
mutable_scalars
if True, the values which are normally assignable to this attribute can mutate,
and need to be compared against a copy of their original contents in order to
detect changes on the parent instance
"""
self.class_ = class_
self.manager = manager
self.key = key
self.callable_ = callable_
self.trackparent = trackparent
self.mutable_scalars = mutable_scalars
if mutable_scalars:
class_._sa_has_mutable_scalars = True
self.copy = None
if compare_function is None:
self.is_equal = lambda x,y: x == y
else:
self.is_equal = compare_function
self.extensions = util.to_list(extension or [])
def commit_to_state(self, state, value=NO_VALUE):
"""commit the object's current state to its 'committed' state."""
if value is NO_VALUE:
if self.key in state.dict:
value = state.dict[self.key]
if value is not NO_VALUE:
state.committed_state[self.key] = self.copy(value)
def hasparent(self, state, optimistic=False):
"""Return the boolean value of a `hasparent` flag attached to the given item.
The `optimistic` flag determines what the default return value
should be if no `hasparent` flag can be located.
As this function is used to determine if an instance is an
*orphan*, instances that were loaded from storage should be
assumed to not be orphans, until a True/False value for this
flag is set.
An instance attribute that is loaded by a callable function
will also not have a `hasparent` flag.
"""
return state.parents.get(id(self), optimistic)
def sethasparent(self, state, value):
"""Set a boolean flag on the given item corresponding to
whether or not it is attached to a parent object via the
attribute represented by this ``InstrumentedAttribute``.
"""
state.parents[id(self)] = value
def get_history(self, state, passive=False):
current = self.get(state, passive=passive)
if current is PASSIVE_NORESULT:
return None
return AttributeHistory(self, state, current, passive=passive)
def set_callable(self, state, callable_, clear=False):
"""Set a callable function for this attribute on the given object.
This callable will be executed when the attribute is next
accessed, and is assumed to construct part of the instances
previously stored state. When its value or values are loaded,
they will be established as part of the instance's *committed
state*. While *trackparent* information will be assembled for
these instances, attribute-level event handlers will not be
fired.
The callable overrides the class level callable set in the
``InstrumentedAttribute` constructor.
"""
if clear:
self.clear(state)
if callable_ is None:
self.initialize(state)
else:
state.callables[self] = callable_
def _get_callable(self, state):
if self in state.callables:
return state.callables[self]
elif self.callable_ is not None:
return self.callable_(state.obj())
else:
return None
def reset(self, state):
"""Remove any per-instance callable functions corresponding to
this ``InstrumentedAttribute``'s attribute from the given
object, and remove this ``InstrumentedAttribute``'s attribute
from the given object's dictionary.
"""
try:
del state.callables[self]
except KeyError:
pass
self.clear(state)
def clear(self, state):
"""Remove this ``InstrumentedAttribute``'s attribute from the given object's dictionary.
Subsequent calls to ``getattr(obj, key)`` will raise an
``AttributeError`` by default.
"""
try:
del state.dict[self.key]
except KeyError:
pass
def check_mutable_modified(self, state):
return False
def initialize(self, state):
"""Initialize this attribute on the given object instance with an empty value."""
state.dict[self.key] = None
return None
def get(self, state, passive=False):
"""Retrieve a value from the given object.
If a callable is assembled on this object's attribute, and
passive is False, the callable will be executed and the
resulting value will be set as the new value for this attribute.
"""
try:
return state.dict[self.key]
except KeyError:
# if an instance-wide "trigger" was set, call that
# and start again
if state.trigger:
state.call_trigger()
return self.get(state, passive=passive)
callable_ = self._get_callable(state)
if callable_ is not None:
if passive:
return PASSIVE_NORESULT
value = callable_()
if value is not ATTR_WAS_SET:
return self.set_committed_value(state, value)
else:
return state.dict[self.key]
else:
# Return a new, empty value
return self.initialize(state)
def append(self, state, value, initiator):
self.set(state, value, initiator)
def remove(self, state, value, initiator):
self.set(state, None, initiator)
def set(self, state, value, initiator):
raise NotImplementedError()
def set_committed_value(self, state, value):
"""set an attribute value on the given instance and 'commit' it.
this indicates that the given value is the "persisted" value,
and history will be logged only if a newly set value is not
equal to this value.
this is typically used by deferred/lazy attribute loaders
to set object attributes after the initial load.
"""
if state.committed_state is not None:
self.commit_to_state(state, value)
# remove per-instance callable, if any
state.callables.pop(self, None)
state.dict[self.key] = value
return value
def set_raw_value(self, state, value):
state.dict[self.key] = value
return value
def fire_append_event(self, state, value, initiator):
state.modified = True
if self.trackparent and value is not None:
self.sethasparent(value._state, True)
obj = state.obj()
for ext in self.extensions:
ext.append(obj, value, initiator or self)
def fire_remove_event(self, state, value, initiator):
state.modified = True
if self.trackparent and value is not None:
self.sethasparent(value._state, False)
obj = state.obj()
for ext in self.extensions:
ext.remove(obj, value, initiator or self)
def fire_replace_event(self, state, value, previous, initiator):
state.modified = True
if self.trackparent:
if value is not None:
self.sethasparent(value._state, True)
if previous is not None:
self.sethasparent(previous._state, False)
obj = state.obj()
for ext in self.extensions:
ext.set(obj, value, previous, initiator or self)
class ScalarAttributeImpl(AttributeImpl):
"""represents a scalar value-holding InstrumentedAttribute."""
def __init__(self, class_, manager, key, callable_, copy_function=None, compare_function=None, mutable_scalars=False, **kwargs):
super(ScalarAttributeImpl, self).__init__(class_, manager, key,
callable_, compare_function=compare_function, mutable_scalars=mutable_scalars, **kwargs)
if copy_function is None:
copy_function = self.__copy
self.copy = copy_function
def __copy(self, item):
# scalar values are assumed to be immutable unless a copy function
# is passed
return item
def delete(self, state):
del state.dict[self.key]
state.modified=True
def check_mutable_modified(self, state):
if self.mutable_scalars:
h = self.get_history(state, passive=True)
if h is not None and h.is_modified():
state.modified = True
return True
else:
return False
else:
return False
def set(self, state, value, initiator):
"""Set a value on the given object.
`initiator` is the ``InstrumentedAttribute`` that initiated the
``set()` operation and is used to control the depth of a circular
setter operation.
"""
if initiator is self:
return
# if an instance-wide "trigger" was set, call that
if state.trigger:
state.call_trigger()
state.dict[self.key] = value
state.modified=True
type = property(lambda self: self.property.columns[0].type)
class ScalarObjectAttributeImpl(ScalarAttributeImpl):
"""represents a scalar class-instance holding InstrumentedAttribute.
Adds events to delete/set operations.
"""
def __init__(self, class_, manager, key, callable_, trackparent=False, extension=None, copy_function=None, compare_function=None, mutable_scalars=False, **kwargs):
super(ScalarObjectAttributeImpl, self).__init__(class_, manager, key,
callable_, trackparent=trackparent, extension=extension,
compare_function=compare_function, mutable_scalars=mutable_scalars, **kwargs)
if compare_function is None:
self.is_equal = identity_equal
def delete(self, state):
old = self.get(state)
del state.dict[self.key]
self.fire_remove_event(state, old, self)
def set(self, state, value, initiator):
"""Set a value on the given object.
`initiator` is the ``InstrumentedAttribute`` that initiated the
``set()` operation and is used to control the depth of a circular
setter operation.
"""
if initiator is self:
return
# if an instance-wide "trigger" was set, call that
if state.trigger:
state.call_trigger()
old = self.get(state)
state.dict[self.key] = value
self.fire_replace_event(state, value, old, initiator)
class CollectionAttributeImpl(AttributeImpl):
"""A collection-holding attribute that instruments changes in membership.
InstrumentedCollectionAttribute holds an arbitrary, user-specified
container object (defaulting to a list) and brokers access to the
CollectionAdapter, a "view" onto that object that presents consistent
bag semantics to the orm layer independent of the user data implementation.
"""
def __init__(self, class_, manager, key, callable_, typecallable=None, trackparent=False, extension=None, copy_function=None, compare_function=None, **kwargs):
super(CollectionAttributeImpl, self).__init__(class_, manager,
key, callable_, trackparent=trackparent, extension=extension,
compare_function=compare_function, **kwargs)
if copy_function is None:
copy_function = self.__copy
self.copy = copy_function
if typecallable is None:
typecallable = list
self.collection_factory = \
collections._prepare_instrumentation(typecallable)
self.collection_interface = \
util.duck_type_collection(self.collection_factory())
def __copy(self, item):
return [y for y in list(collections.collection_adapter(item))]
def delete(self, state):
if self.key not in state.dict:
return
state.modified = True
collection = self.get_collection(state)
collection.clear_with_event()
del state.dict[self.key]
def initialize(self, state):
"""Initialize this attribute on the given object instance with an empty collection."""
_, user_data = self._build_collection(state)
state.dict[self.key] = user_data
return user_data
def append(self, state, value, initiator):
if initiator is self:
return
collection = self.get_collection(state)
collection.append_with_event(value, initiator)
def remove(self, state, value, initiator):
if initiator is self:
return
collection = self.get_collection(state)
collection.remove_with_event(value, initiator)
def set(self, state, value, initiator):
"""Set a value on the given object.
`initiator` is the ``InstrumentedAttribute`` that initiated the
``set()` operation and is used to control the depth of a circular
setter operation.
"""
if initiator is self:
return
setting_type = util.duck_type_collection(value)
if value is None or setting_type != self.collection_interface:
raise exceptions.ArgumentError(
"Incompatible collection type on assignment: %s is not %s-like" %
(type(value).__name__, self.collection_interface.__name__))
if hasattr(value, '_sa_adapter'):
value = list(getattr(value, '_sa_adapter'))
elif setting_type == dict:
value = value.values()
# if an instance-wide "trigger" was set, call that
if state.trigger:
state.call_trigger()
old = self.get(state)
old_collection = self.get_collection(state, old)
new_collection, user_data = self._build_collection(state)
idset = util.IdentitySet
constants = idset(old_collection or []).intersection(value or [])
additions = idset(value or []).difference(constants)
removals = idset(old_collection or []).difference(constants)
for member in value or []:
if member in additions:
new_collection.append_with_event(member)
elif member in constants:
new_collection.append_without_event(member)
state.dict[self.key] = user_data
state.modified = True
# mark all the orphaned elements as detached from the parent
if old_collection:
for member in removals:
old_collection.remove_with_event(member)
old_collection.unlink(old)
def set_committed_value(self, state, value):
"""Set an attribute value on the given instance and 'commit' it."""
collection, user_data = self._build_collection(state)
self._load_collection(state, value or [], emit_events=False,
collection=collection)
value = user_data
if state.committed_state is not None:
self.commit_to_state(state, value)
# remove per-instance callable, if any
state.callables.pop(self, None)
state.dict[self.key] = value
return value
def _build_collection(self, state):
user_data = self.collection_factory()
collection = collections.CollectionAdapter(self, state, user_data)
return collection, user_data
def _load_collection(self, state, values, emit_events=True, collection=None):
collection = collection or self.get_collection(state)
if values is None:
return
elif emit_events:
for item in values:
collection.append_with_event(item)
else:
for item in values:
collection.append_without_event(item)
def get_collection(self, state, user_data=None):
if user_data is None:
user_data = self.get(state)
try:
return getattr(user_data, '_sa_adapter')
except AttributeError:
collections.CollectionAdapter(self, state, user_data)
return getattr(user_data, '_sa_adapter')
class GenericBackrefExtension(interfaces.AttributeExtension):
"""An extension which synchronizes a two-way relationship.
A typical two-way relationship is a parent object containing a
list of child objects, where each child object references the
parent. The other are two objects which contain scalar references
to each other.
"""
def __init__(self, key):
self.key = key
def set(self, obj, child, oldchild, initiator):
if oldchild is child:
return
if oldchild is not None:
# With lazy=None, there's no guarantee that the full collection is
# present when updating via a backref.
impl = getattr(oldchild.__class__, self.key).impl
try:
impl.remove(oldchild._state, obj, initiator)
except (ValueError, KeyError, IndexError):
pass
if child is not None:
getattr(child.__class__, self.key).impl.append(child._state, obj, initiator)
def append(self, obj, child, initiator):
getattr(child.__class__, self.key).impl.append(child._state, obj, initiator)
def remove(self, obj, child, initiator):
getattr(child.__class__, self.key).impl.remove(child._state, obj, initiator)
class InstanceState(object):
"""tracks state information at the instance level."""
__slots__ = 'class_', 'obj', 'dict', 'committed_state', 'modified', 'trigger', 'callables', 'parents', 'instance_dict', '_strong_obj'
def __init__(self, obj):
self.class_ = obj.__class__
self.obj = weakref.ref(obj, self.__cleanup)
self.dict = obj.__dict__
self.committed_state = None
self.modified = False
self.trigger = None
self.callables = {}
self.parents = {}
self.instance_dict = None
def __cleanup(self, ref):
if self.instance_dict is None or self.instance_dict() is None:
return
instance_dict = self.instance_dict()
# the mutexing here is based on the assumption that gc.collect()
# may be firing off cleanup handlers in a different thread than that
# which is normally operating upon the instance dict.
instance_dict._mutex.acquire()
try:
# if instance_dict de-refed us, or it called our
# _resurrect, return
if self.instance_dict is None or self.instance_dict() is None or self.obj() is not None:
return
self.__resurrect(instance_dict)
finally:
instance_dict._mutex.release()
def _check_resurrect(self, instance_dict):
instance_dict._mutex.acquire()
try:
return self.obj() or self.__resurrect(instance_dict)
finally:
instance_dict._mutex.release()
def __resurrect(self, instance_dict):
if self.modified or self.class_._sa_attribute_manager._is_modified(self):
# store strong ref'ed version of the object; will revert
# to weakref when changes are persisted
obj = self.class_._sa_attribute_manager.new_instance(self.class_, state=self)
self.obj = weakref.ref(obj, self.__cleanup)
self._strong_obj = obj
obj.__dict__.update(self.dict)
self.dict = obj.__dict__
return obj
else:
del instance_dict[self.dict['_instance_key']]
return None
def __getstate__(self):
return {'committed_state':self.committed_state, 'parents':self.parents, 'modified':self.modified, 'instance':self.obj()}
def __setstate__(self, state):
self.committed_state = state['committed_state']
self.parents = state['parents']
self.modified = state['modified']
self.obj = weakref.ref(state['instance'])
self.class_ = self.obj().__class__
self.dict = self.obj().__dict__
self.callables = {}
self.trigger = None
def call_trigger(self):
trig = self.trigger
self.trigger = None
trig()
def commit(self, manager, obj):
self.committed_state = {}
self.modified = False
for attr in manager.managed_attributes(obj.__class__):
attr.impl.commit_to_state(self)
# remove strong ref
self._strong_obj = None
def rollback(self, manager, obj):
if not self.committed_state:
manager._clear(obj)
else:
for attr in manager.managed_attributes(obj.__class__):
if attr.impl.key in self.committed_state:
if not hasattr(attr.impl, 'get_collection'):
obj.__dict__[attr.impl.key] = self.committed_state[attr.impl.key]
else:
collection = attr.impl.get_collection(self)
collection.clear_without_event()
for item in self.committed_state[attr.impl.key]:
collection.append_without_event(item)
else:
if attr.impl.key in self.dict:
del self.dict[attr.impl.key]
class InstanceDict(UserDict.UserDict):
"""similar to WeakValueDictionary, but wired towards 'state' objects."""
def __init__(self, *args, **kw):
self._wr = weakref.ref(self)
# RLock because the mutex is used by a cleanup
# handler, which can be called at any time (including within an already mutexed block)
self._mutex = threading.RLock()
UserDict.UserDict.__init__(self, *args, **kw)
def __getitem__(self, key):
state = self.data[key]
o = state.obj()
if o is None:
o = state._check_resurrect(self)
if o is None:
raise KeyError, key
return o
def __contains__(self, key):
try:
state = self.data[key]
o = state.obj()
if o is None:
o = state._check_resurrect(self)
except KeyError:
return False
return o is not None
def has_key(self, key):
return key in self
def __repr__(self):
return "<InstanceDict at %s>" % id(self)
def __setitem__(self, key, value):
if key in self.data:
self._mutex.acquire()
try:
if key in self.data:
self.data[key].instance_dict = None
finally:
self._mutex.release()
self.data[key] = value._state
value._state.instance_dict = self._wr
def __delitem__(self, key):
state = self.data[key]
state.instance_dict = None
del self.data[key]
def get(self, key, default=None):
try:
state = self.data[key]
except KeyError:
return default
else:
o = state.obj()
if o is None:
# This should only happen
return default
else:
return o
def items(self):
L = []
for key, state in self.data.items():
o = state.obj()
if o is not None:
L.append((key, o))
return L
def iteritems(self):
for state in self.data.itervalues():
value = state.obj()
if value is not None:
yield value._instance_key, value
def iterkeys(self):
return self.data.iterkeys()
def __iter__(self):
return self.data.iterkeys()
def __len__(self):
return len(self.values())
def itervalues(self):
for state in self.data.itervalues():
obj = state.obj()
if obj is not None:
yield obj
def values(self):
L = []
for state in self.data.values():
o = state.obj()
if o is not None:
L.append(o)
return L
def popitem(self):
raise NotImplementedError()
def pop(self, key, *args):
raise NotImplementedError()
def setdefault(self, key, default=None):
raise NotImplementedError()
def update(self, dict=None, **kwargs):
raise NotImplementedError()
def copy(self):
raise NotImplementedError()
class AttributeHistory(object):
"""Calculate the *history* of a particular attribute on a
particular instance.
"""
NO_VALUE = object()
def __init__(self, attr, state, current, passive=False):
self.attr = attr
# get the "original" value. if a lazy load was fired when we got
# the 'current' value, this "original" was also populated just
# now as well (therefore we have to get it second)
if state.committed_state:
original = state.committed_state.get(attr.key, NO_VALUE)
else:
original = NO_VALUE
if hasattr(attr, 'get_collection'):
self._current = current
if original is NO_VALUE:
s = util.IdentitySet([])
else:
s = util.IdentitySet(original)
# FIXME: the tests have an assumption on the collection's ordering
self._added_items = util.OrderedIdentitySet()
self._unchanged_items = util.OrderedIdentitySet()
self._deleted_items = util.OrderedIdentitySet()
if current:
collection = attr.get_collection(state, current)
for a in collection:
if a in s:
self._unchanged_items.add(a)
else:
self._added_items.add(a)
for a in s:
if a not in self._unchanged_items:
self._deleted_items.add(a)
else:
self._current = [current]
if attr.is_equal(current, original) is True:
self._unchanged_items = [current]
self._added_items = []
self._deleted_items = []
else:
self._added_items = [current]
if original is not NO_VALUE and original is not None:
self._deleted_items = [original]
else:
self._deleted_items = []
self._unchanged_items = []
def __iter__(self):
return iter(self._current)
def is_modified(self):
return len(self._deleted_items) > 0 or len(self._added_items) > 0
def added_items(self):
return list(self._added_items)
def unchanged_items(self):
return list(self._unchanged_items)
def deleted_items(self):
return list(self._deleted_items)
class AttributeManager(object):
"""Allow the instrumentation of object attributes."""
def __init__(self):
# will cache attributes, indexed by class objects
self._inherited_attribute_cache = weakref.WeakKeyDictionary()
self._noninherited_attribute_cache = weakref.WeakKeyDictionary()
def clear_attribute_cache(self):
self._attribute_cache.clear()
def rollback(self, *obj):
"""Retrieve the committed history for each object in the given
list, and rolls back the attributes each instance to their
original value.
"""
for o in obj:
o._state.rollback(self, o)
def _clear(self, obj):
for attr in self.managed_attributes(obj.__class__):
try:
del obj.__dict__[attr.impl.key]
except KeyError:
pass
def commit(self, *obj):
"""Establish the "committed state" for each object in the given list."""
for o in obj:
o._state.commit(self, o)
def managed_attributes(self, class_):
"""Return a list of all ``InstrumentedAttribute`` objects
associated with the given class.
"""
try:
# TODO: move this collection onto the class itself?
return self._inherited_attribute_cache[class_]
except KeyError:
if not isinstance(class_, type):
raise TypeError(repr(class_) + " is not a type")
inherited = [v for v in [getattr(class_, key, None) for key in dir(class_)] if isinstance(v, InstrumentedAttribute)]
self._inherited_attribute_cache[class_] = inherited
return inherited
def noninherited_managed_attributes(self, class_):
try:
# TODO: move this collection onto the class itself?
return self._noninherited_attribute_cache[class_]
except KeyError:
if not isinstance(class_, type):
raise TypeError(repr(class_) + " is not a type")
noninherited = [v for v in [getattr(class_, key, None) for key in list(class_.__dict__)] if isinstance(v, InstrumentedAttribute)]
self._noninherited_attribute_cache[class_] = noninherited
return noninherited
def is_modified(self, obj):
return self._is_modified(obj._state)
def _is_modified(self, state):
if state.modified:
return True
elif getattr(state.class_, '_sa_has_mutable_scalars', False):
for attr in self.managed_attributes(state.class_):
if getattr(attr.impl, 'mutable_scalars', False) and attr.impl.check_mutable_modified(state):
return True
else:
return False
else:
return False
def get_history(self, obj, key, **kwargs):
"""Return a new ``AttributeHistory`` object for the given
attribute on the given object.
"""
return getattr(obj.__class__, key).impl.get_history(obj._state, **kwargs)
def get_as_list(self, obj, key, passive=False):
"""Return an attribute of the given name from the given object.
If the attribute is a scalar, return it as a single-item list,
otherwise return a collection based attribute.
If the attribute's value is to be produced by an unexecuted
callable, the callable will only be executed if the given
`passive` flag is False.
"""
attr = getattr(obj.__class__, key).impl
state = obj._state
x = attr.get(state, passive=passive)
if x is PASSIVE_NORESULT:
return []
elif hasattr(attr, 'get_collection'):
return list(attr.get_collection(state, x))
elif isinstance(x, list):
return x
else:
return [x]
def trigger_history(self, obj, callable):
"""Clear all managed object attributes and places the given
`callable` as an attribute-wide *trigger*, which will execute
upon the next attribute access, after which the trigger is
removed.
"""
s = obj._state
self._clear(obj)
s.committed_state = None
s.trigger = callable
def untrigger_history(self, obj):
"""Remove a trigger function set by trigger_history.
Does not restore the previous state of the object.
"""
obj._state.trigger = None
def has_trigger(self, obj):
"""Return True if the given object has a trigger function set
by ``trigger_history()``.
"""
return obj._state.trigger is not None
def reset_instance_attribute(self, obj, key):
"""Remove any per-instance callable functions corresponding to
given attribute `key` from the given object, and remove this
attribute from the given object's dictionary.
"""
attr = getattr(obj.__class__, key)
attr.impl.reset(obj._state)
def is_class_managed(self, class_, key):
"""Return True if the given `key` correponds to an
instrumented property on the given class.
"""
return hasattr(class_, key) and isinstance(getattr(class_, key), InstrumentedAttribute)
def has_parent(self, class_, obj, key, optimistic=False):
return getattr(class_, key).impl.hasparent(obj._state, optimistic=optimistic)
def init_instance_attribute(self, obj, key, callable_=None, clear=False):
"""Initialize an attribute on an instance to either a blank
value, cancelling out any class- or instance-level callables
that were present, or if a `callable` is supplied set the
callable to be invoked when the attribute is next accessed.
"""
getattr(obj.__class__, key).impl.set_callable(obj._state, callable_, clear=clear)
def _create_prop(self, class_, key, uselist, callable_, typecallable, useobject, **kwargs):
"""Create a scalar property object, defaulting to
``InstrumentedAttribute``, which will communicate change
events back to this ``AttributeManager``.
"""
if kwargs.pop('dynamic', False):
from sqlalchemy.orm import dynamic
return dynamic.DynamicAttributeImpl(class_, self, key, typecallable, **kwargs)
elif uselist:
return CollectionAttributeImpl(class_, self, key,
callable_,
typecallable,
**kwargs)
elif useobject:
return ScalarObjectAttributeImpl(class_, self, key, callable_,
**kwargs)
else:
return ScalarAttributeImpl(class_, self, key, callable_,
**kwargs)
def manage(self, obj):
if not hasattr(obj, '_state'):
obj._state = InstanceState(obj)
def new_instance(self, class_, state=None):
"""create a new instance of class_ without its __init__() method being called."""
s = class_.__new__(class_)
if state:
s._state = state
else:
s._state = InstanceState(s)
return s
def register_class(self, class_, extra_init=None, on_exception=None):
"""decorate the constructor of the given class to establish attribute
management on new instances."""
# do a sweep first, this also helps some attribute extensions
# (like associationproxy) become aware of themselves at the
# class level
self.unregister_class(class_)
oldinit = None
doinit = False
class_._sa_attribute_manager = self
def init(instance, *args, **kwargs):
instance._state = InstanceState(instance)
if extra_init:
extra_init(class_, oldinit, instance, args, kwargs)
if doinit:
try:
oldinit(instance, *args, **kwargs)
except:
if on_exception:
on_exception(class_, oldinit, instance, args, kwargs)
raise
# override oldinit
oldinit = class_.__init__
if oldinit is None or not hasattr(oldinit, '_oldinit'):
init._oldinit = oldinit
class_.__init__ = init
# if oldinit is already one of our 'init' methods, replace it
elif hasattr(oldinit, '_oldinit'):
init._oldinit = oldinit._oldinit
class_.__init = init
oldinit = oldinit._oldinit
if oldinit is not None:
doinit = oldinit is not object.__init__
try:
init.__name__ = oldinit.__name__
init.__doc__ = oldinit.__doc__
except:
# cant set __name__ in py 2.3 !
pass
def unregister_class(self, class_):
if hasattr(class_, '__init__') and hasattr(class_.__init__, '_oldinit'):
if class_.__init__._oldinit is not None:
class_.__init__ = class_.__init__._oldinit
else:
delattr(class_, '__init__')
for attr in self.noninherited_managed_attributes(class_):
delattr(class_, attr.impl.key)
self._inherited_attribute_cache.pop(class_,None)
self._noninherited_attribute_cache.pop(class_,None)
def register_attribute(self, class_, key, uselist, useobject, callable_=None, **kwargs):
"""Register an attribute at the class level to be instrumented
for all instances of the class.
"""
# firt invalidate the cache for the given class
# (will be reconstituted as needed, while getting managed attributes)
self._inherited_attribute_cache.pop(class_, None)
self._noninherited_attribute_cache.pop(class_, None)
typecallable = kwargs.pop('typecallable', None)
if isinstance(typecallable, InstrumentedAttribute):
typecallable = None
comparator = kwargs.pop('comparator', None)
setattr(class_, key, InstrumentedAttribute(self._create_prop(class_, key, uselist, callable_, useobject=useobject,
typecallable=typecallable, **kwargs), comparator=comparator))
def set_raw_value(self, instance, key, value):
getattr(instance.__class__, key).impl.set_raw_value(instance._state, value)
def set_committed_value(self, instance, key, value):
getattr(instance.__class__, key).impl.set_committed_value(instance._state, value)
def init_collection(self, instance, key):
"""Initialize a collection attribute and return the collection adapter."""
attr = getattr(instance.__class__, key).impl
state = instance._state
user_data = attr.initialize(state)
return attr.get_collection(state, user_data)
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