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# attributes.py - manages object attributes
# Copyright (C) 2005 Michael Bayer mike_mp@zzzcomputing.com
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
import sqlalchemy.util as util
import weakref
class SmartProperty(object):
"""attaches AttributeManager functionality to the property accessors of a class. all instances
of the class will retrieve and modify their properties via an AttributeManager."""
def __init__(self, manager):
self.manager = manager
def attribute_registry(self):
return self.manager
def property(self, key, uselist):
def set_prop(obj, value):
if uselist:
self.attribute_registry().set_list_attribute(obj, key, value)
else:
self.attribute_registry().set_attribute(obj, key, value)
def del_prop(obj):
if uselist:
# TODO: this probably doesnt work right, deleting the list off an item
self.attribute_registry().delete_list_attribute(obj, key)
else:
self.attribute_registry().delete_attribute(obj, key)
def get_prop(obj):
if uselist:
return self.attribute_registry().get_list_attribute(obj, key)
else:
return self.attribute_registry().get_attribute(obj, key)
return property(get_prop, set_prop, del_prop)
class PropHistory(object):
"""manages the value of a particular scalar attribute on a particular object instance."""
# make our own NONE to distinguish from "None"
NONE = object()
def __init__(self, obj, key):
self.obj = obj
self.key = key
self.orig = PropHistory.NONE
def setattr_clean(self, value):
self.obj.__dict__[self.key] = value
def setattr(self, value):
if isinstance(value, list):
raise ("assigning a list to scalar property '%s' on '%s' instance %d" % (self.key, self.obj.__class__.__name__, id(self.obj)))
self.orig = self.obj.__dict__.get(self.key, None)
self.obj.__dict__[self.key] = value
def delattr(self):
self.orig = self.obj.__dict__.get(self.key, None)
self.obj.__dict__[self.key] = None
def rollback(self):
if self.orig is not PropHistory.NONE:
self.obj.__dict__[self.key] = self.orig
self.orig = PropHistory.NONE
def commit(self):
self.orig = PropHistory.NONE
def added_items(self):
if self.orig is not PropHistory.NONE:
return [self.obj.__dict__[self.key]]
else:
return []
def deleted_items(self):
if self.orig is not PropHistory.NONE and self.orig is not None:
return [self.orig]
else:
return []
def unchanged_items(self):
if self.orig is PropHistory.NONE:
return [self.obj.__dict__[self.key]]
else:
return []
class ListElement(util.HistoryArraySet):
"""manages the value of a particular list-based attribute on a particular object instance."""
def __init__(self, obj, key, items = None):
self.obj = obj
self.key = key
util.HistoryArraySet.__init__(self, items)
obj.__dict__[key] = self.data
def list_value_changed(self, obj, key, listval):
pass
def setattr(self, value):
self.obj.__dict__[self.key] = value
self.set_data(value)
def delattr(self, value):
pass
def _setrecord(self, item):
res = util.HistoryArraySet._setrecord(self, item)
if res:
self.list_value_changed(self.obj, self.key, self)
return res
def _delrecord(self, item):
res = util.HistoryArraySet._delrecord(self, item)
if res:
self.list_value_changed(self.obj, self.key, self)
return res
class AttributeManager(object):
"""maintains a set of per-attribute history objects for a set of objects."""
def __init__(self):
self.attribute_history = {}
def value_changed(self, obj, key, value):
pass
def create_prop(self, key, uselist):
return SmartProperty(self).property(key, uselist)
def create_list(self, obj, key, list_):
return ListElement(obj, key, list_)
def get_attribute(self, obj, key):
try:
v = obj.__dict__[key]
except KeyError:
raise AttributeError(key)
if (callable(v)):
v = v()
obj.__dict__[key] = v
return v
def get_list_attribute(self, obj, key):
return self.get_list_history(obj, key)
def set_attribute(self, obj, key, value):
self.get_history(obj, key).setattr(value)
self.value_changed(obj, key, value)
def set_list_attribute(self, obj, key, value):
self.get_list_history(obj, key).setattr(value)
def delete_attribute(self, obj, key):
self.get_history(obj, key).delattr()
self.value_changed(obj, key, value)
def delete_list_attribute(self, obj, key):
pass
def rollback(self, obj = None):
if obj is None:
for attr in self.attribute_history.values():
for hist in attr.values():
hist.rollback()
else:
try:
attributes = self.attribute_history[obj]
for hist in attributes.values():
hist.rollback()
except KeyError:
pass
def commit(self, obj = None):
if obj is None:
for attr in self.attribute_history.values():
for hist in attr.values():
hist.commit()
else:
try:
attributes = self.attribute_history[obj]
for hist in attributes.values():
hist.commit()
except KeyError:
pass
def remove(self, obj):
try:
del self.attribute_history[obj]
except KeyError:
pass
def get_history(self, obj, key):
try:
return self.attribute_history[obj][key]
except KeyError, e:
if e.args[0] is obj:
d = {}
self.attribute_history[obj] = d
p = PropHistory(obj, key)
d[key] = p
return p
else:
p = PropHistory(obj, key)
self.attribute_history[obj][key] = p
return p
def get_list_history(self, obj, key, passive = False):
try:
return self.attribute_history[obj][key]
except KeyError, e:
list_ = obj.__dict__.get(key, None)
if callable(list_):
if passive:
return None
list_ = list_()
if e.args[0] is obj:
d = {}
self.attribute_history[obj] = d
p = self.create_list(obj, key, list_)
d[key] = p
return p
else:
p = self.create_list(obj, key, list_)
self.attribute_history[obj][key] = p
return p
def register_attribute(self, class_, key, uselist):
setattr(class_, key, self.create_prop(key, uselist))
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