Design issue for MVC and database updates

[jocked at chello.se (Joakim Danielson)]

Hello

I'm on my way of implementing my first own application in 
Cocoa/Objective-C.  I've just implemented a window with master-detail 
layout using a NSArrayController that works against a database.

Here is the issue:

I have a function that stores the rows in my array (bound to 
NSArrayController) to the database with insert or update commands. The 
problem is that all old objects get updated in the database even if the 
have not been update in the GUI. So I need some kind of dirty flag to 
keep track of objects that have really changed.

Where should I implement this flag? Can I somehow use NSArrayController 
for this or my controll object?

I would prefer to handle it in the controll layer and not in the model 
layer.

Joakim Danielson