[Zope] Class instances changing address?

[Gabriel Genellina]

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