[Zope] Object reload event?

[Kapil Thangavelu]

On Wed, 2004-03-10 at 17:29, Dylan Jay wrote:
> ----- Original Message ----- 
> From: "Dieter Maurer" <dieter at handshake.de>
> To: "Dylan Jay" <me at dylanjay.com>
> Cc: <zope at zope.org>
> Sent: Thursday, March 11, 2004 7:48 AM
> Subject: Re: [Zope] Object reload event?
> 
> 
> > Dylan Jay wrote at 2004-3-9 16:37 +1100:
> > >I have an object that uses manage_afterAdd to install several subobjects.
> > >When this object is refreshed or zope is started I want to have a method
> run
> > >on each instance of that object to ensure these subobjects are still
> there
> > >and are of the right type. How do I do this?
> >
> > Whenever an object is loaded from ZODB, its "__setstate__" method
> > is called.
> >
> > However, you are severely restricted what you can do in this
> > method:
> >
> >   *  "self" is not acquisition wrapped.
> >
> >      This means, you cannot access the position of the object
> >      inside the Zope object hierarchy.
> >
> >   *  Modification you make to the object may not become persistent.
> 
> Not really suitable then.
> 
> >
> > It is probably better to design a consistency checking script
> > that periodically checks your consistency requirements.
> >
> > Even better would be to prevent your system to become
> > inconsistent (rather than detect inconsistency at a later time).
> 
> It's not so much inconsistency of data that I'm trying to fix but rather to
> make it easier for me to upgrade my more complex objects. I havc a product
> with an object that has a subobject such as a predefined catalog. When a I
> am developing I want to able to check if there is anything new to add to
> that catalog such as a new index. So I guess being able to hook into the
> refresh functionality would be enough.

adding an explicit upgrade method to your developed classes is probably
a better way to go. possibly recording a version number as instance
attribute to do comparison of class v. instance version.

-kapil