[Zope3-Users] Extending interfaces and implementations

[matt wilbert]

I think you might find that zope3 generations address your requirement.

See:
http://svn.zope.org/Zope3/trunk/src/zope/app/generations/README.txt?view=markup

As far as reloads go, it would be very useful, but my understanding is that
it is hard to implement reliably.  My workaround is to do as much
development in your tests as possible, so I can mostly avoid restarts.
Maybe someone else can explain exactly how hard it would be to add reloads.

Matt


On 2/8/06, Behrang Dadsetan <bdadsetan at gmail.com> wrote:
>
> Hi,
>
> when a class is augumented of a new attribute, my understanding is
> that the instances created with the older version of the class will
> not have that attribute. Will the interfaces and methods that are also
> updated to reflect the new attribute will fail on older instances?
>
> Is there any migration tools used to "update" old instances? Does one
> have to rewrite it every time one does an upgrade? I guess one could
> decide to populate that attribute with its default value like most
> systems tend to do.. but what methods would I have handy?
>
> Is a completely different strategy used, like versioning of classes
> with templates and class method implementations linked to the specific
> version of the instance's class?
>
> Maybe the problem I am talking about only concerns ZODB based
> repositories of objects and not RDBs. Does everyone use RDBs?
>
> Also how difficult would it be to add a runtime "reload" of zcml
> configurations or python modules? Was it a design decision not to have
> this handy, or would such a feature be interesting for the community?
>
> Thanks
> Ben.
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