What do you bind NSArrayController's Managed Object Context to in Xcode 4?

Question

I am trying to build an document-based application for beer reviewing that allows you to enter your notes. I have built the model in Core Data and the view in Interface Builder. Following some Xcode 3-based tutorials, I am told to connect the new NSArrayController to the managedObjectContext of File's Owner. If I try and do this in Xcode 4, a circled exclamation point comes up next to "Model Key Path" in the inspector for the NSArrayController.

I can actually load the .xib file in Interface Builder in Xcode 3, make that connection, and then build it in Xcode 4 and it runs, but every field raises a validation error.

The model has an entity named Scoresheet, which has a property named date, which is an NSDate. But if I link it to the value of an NSDatePicker and try to save it to disk, it says I have "multiple validation errors." How can that be? They are both NSDates, right? Actually, I have the same problem with bindings to everything; none of my UI objects will work with my model.

The only thing I can figure is that there is something going wrong in the connection between the File's Owner and the NSArrayController.

I haven't written any code at this point, because I'm of the understanding I shouldn't have to just to link UI fields and core data. Is it different because I am using a document-based application? (I can't get it to work in a single window app, either.)

An answer of "don't use Core Data" isn't going to be productive; I know I can just fall back on a regular data object. I would like to figure this out in the context of Core Data if possible.

TIA!

(Update: this question seems to be vexing a lot of people. I have consulted the Zarra book on Core Data, the Hillegas book on Cocoa Programming, and two O'Reilly books. They all seem to be based on Xcode 3.)

Answer 1

NSPersistentDocument has it's own managed object context, and you should bind the NSArrayController in your document's xib file to that managed object context.

For example, if your document class is called MyDocument, then Xcode will automatically generate a MyDocument.h / .m / .xib for you. In the .xib, the File's Owner is an instance of your MyDocument class, and you can bind the NSArrayController to this, with the binding File's Owner -> managedObjectContext.