[ZODB-Dev] Re: Class Versioning

[Chris S]

On 7/14/06, Chris S <chrisspen at gmail.com> wrote:
> I'm trying to detect a disparity between an instance __version__ and a
> class __version__, signifying a class upgrade. However, I'm not sure
> why the following code doesn't work.
>
> class Foo(Persistent):
>     __version__ = 1.0
>
>     def __setstate__(self, state):
>         Persistent.__setstate__( self, state )
>         print self.__version__, type(self).__version__
>         if self.__version__ != type(self).__version__:
>             print 'upgrading'
>         self.__version__ = type(self).__version__
>
> If I persist an instance of foo, close the db, change the class
> version, open my db then reload my instance, the version numbers are
> always equal and it never detects an upgrade. Why isn't ZODB saving
> the instance's __version__ attribute? Shouldn't the last line save
> __version__ in the instance's __dict__, which should then be different
> from the __class__.__version__?
>
> Chris

Nevermind, I just realized I have to do self.__version__ =
self.__version__ at the beginning of __setstate__ or else the instance
never stores a local __version__, causing __class__.__version__ to be
used instead.

Chris