At Friday 20/1/2006 20:07, Jeff Gentry wrote:

As background, the primary class (A) maintains a handle to an instance of another class (B) which handles interaction w/ a psycopg db controller. Class A also will instantiate several instances of Class C and as part of the construction will pass it the handle to class B. So in summary, A has a B and has 1:n C's, and C has a reference to B. A & B have physical representations in the ZMI, while instances of C are 'virtual'.

If you follow these rules you should be safe: - Never store a reference to a persistent object inside another persistent object; use its id or path to retrieve it when needed. - Never store a reference to a persistent object inside a non-persistent object. - If a persistent object "owns" some other persistent objects, make the first an ObjectManager. - Let Zope manage transactions, and avoid bare try/excepts Of course you can break the rules if you really really know what you are doing but they are a good starting point. And reading about how persistence works is a big help (it appears you've already read it, I think). Gabriel Genellina Softlab SRL