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# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
#
import sys
from util.decorators import DecoratorWithArgs
class Persistent(type):
'''Metaclass providing object persistence'''
def __init__(cls, name, bases, dct):
super(Persistent, cls).__init__(name, bases, dct)
setattr(cls, '__dirty__', False)
setattr(cls, '__properties__', filter(_is_persistent, dct.iteritems()))
from util.journalpickler import dumps, loads
setattr(cls, 'dumps', dumps)
setattr(cls, 'loads', loads)
@DecoratorWithArgs
def PersistentProperty(function, default = None):
'''Decorator to set persistent properties'''
keys = 'fset', 'fdel'
func_locals = {'doc':function.__doc__}
def fgetter(obj, name, getter, default_value):
attr_name = '_' + obj.__class__.__name__ + '__' + name
if not hasattr(obj, attr_name):
setattr(obj, attr_name, default_value(obj))
return getter(obj)
def fsetter(obj, name, setter, value):
setattr(obj, '__dirty__', True)
return setter(obj, value)
def introspect(frame, event, arg):
if event == 'return':
locals = frame.f_locals
func_locals.update(dict((k,locals.get(k)) for k in keys))
if locals.has_key('fset'):
func_locals['fset'] = \
lambda obj, value : fsetter(obj, function.__name__, locals['fset'], value)
if default != None:
get_function = \
lambda obj : fgetter(obj, function.__name__, locals['fget'], lambda x : default)
else:
get_function = \
lambda obj : fgetter(obj, function.__name__, locals['fget'], lambda x : None)
get_function.decorator = PersistentProperty # tag the getter so we can id
# the decorator. Yeah, it's ugly.
func_locals['fget'] = get_function
sys.settrace(None)
return introspect
sys.settrace(introspect)
function()
return property(**func_locals)
# a wee bit ugly
def _is_persistent(item):
'''check if property is decorated with PersistentProperty decorator'''
prop = item[1]
return type(prop) is property and \
hasattr(prop.fget, 'decorator') and \
prop.fget.decorator is PersistentProperty
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