Hello Chris Spencer,
Saturday, October 29, 2005, 7:16:43 AM, you wrote:
CS> Would it be possible to support some system of class versioning in ZODB,
CS> to aid to handling modifications to source code? For instance, suppose
CS> each class definition has a __version__ attribute. Upon serialization,
CS> this version is saved for each instance. Then, if the class is updated,
CS> signified by incrementing the class's __version__, ZODB could take
CS> action, for example, by executing an optional __upgrade_to_x(self) in
CS> the new class definition.
you can easily derive your own class from Persistent class, and add some
system of class versioning
to them.
for example ( untested )
class Persistent(_Persistent):
# attributes for version tag support
_class_version = None
_class_tag = None
_version_tag = None
def __class_init__(self): # works only for extension classes
tags = [ self._class_version ]
for base in self.__bases__:
if hasattr( base, '_class_tag' ):
tags.append( base._class_tag )
self._class_tag = hash( tuple(tags) )
def __setstate__( self, state ):
_Persistent.__setstate__( self, state )
if self.tagChanged():
self.doSomething()
def doSomething(self):
self._version_tag = self._class_tag
def tagChanged(self):
return self._version_tag <> self._class_tag
class A(Persistent):
_class_version = 1.3
class B(A):
_class_version = 1.45
--
Best regards,
Victor Safronovich
NauMen.NauDoc.SoftwareDeveloper http://www.naumen.ru
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