[Zope] [ADVANCED] How do YOU guys do many-to-many in Zope without relational?

Casey Duncan c.duncan@nlada.org
Tue, 23 Oct 2001 08:45:32 -0400

On Monday 22 October 2001 05:40 pm, Max M allegedly wrote:
> > From: Casey Duncan [mailto:c.duncan@nlada.org]
> >
> > They way to do this is to create a lines property in the student
> > and store
> > the ids of the related subjects there. You use a ZCatalog and a
> > keyword index
> > on this property to quickly find which students belong to which subject.
> Again only if the id's are unique all over the site.
> > 2. Assign another fixed key as a property (or general attribute) of the
> > subject for use as the unique identifier and don't ever change it for the
> > life of the object.
> There allready exist such a key for each object in the ZODB called the oid,
> but I don't think that it's easy to get at through normal means. I am not
> even shure that it's "allowed" to use it for anything.

I would not use oids, they can change for instance if you export and 
re-import objects.

> > You will need to use a ZCatalog to make
> > lookups on this
> > id efficient, but this would allow you to put the object anywhere
> > you like,
> > and rename them without screwing up the relationships. Only
> > deletion would
> > break it.
> Deletion always has a tendency to do this. I need triggers in the ZODB :-)
> regards Max M

ObjectManager has such a mechanism. It calls manage_beforeDelete on an object 
before it is deleted.

  Casey Duncan, Sr. Web Developer
  National Legal Aid and Defender Association