I have an array of NSDictionaries and a NSDictionary iVar (*selectedDictionary) that points to one of the array's objects. *selectedDictionary points to a different object every time the user selects a different row in a NSTableView. Several GUI controls are binded to the selectedDictionary instance (IB).
I just want to make the NSDocument dirty (edited) every time the user alters the above controls. I think using Key Value Observing for ALL the objects in the array and all their kaypaths, is a bit insufficient. Any suggestions?
Thanks
NSDocument's support for marking a document as dirty comes directly from the NSUndoManager. The easiest way to change the document to dirty is to do an implementation of Undo, and this is basically going to mean doing the undo inside of the model class that the document is using (or the subclass of NSDocument if you choose to handle all storage directly in there).
Apple has documentation on this here: http://developer.apple.com/library/ios/#documentation/cocoa/Conceptual/UndoArchitecture/Articles/AppKitUndo.html
Since you indicate you have an array of dictionaries, that's going to make it a bit more work to implement, but once you have nailed that, you'll be in good shape.
Alternatively, if you don't want to go with the freebie support provided by NSDocument and NSUndoManager, you can manually handle undo and use the updateChangeCount: method to modify the internal understanding of whether changes have occurred. This takes some work, and likely is a lot less useful than just setting up undo correctly.
As for the efficiency of observing all the objects in the array, I wouldn't worry about it unless you have profiled it and found it to be inefficient. KVO is really pretty darned efficient and we regularly observe multiple values in every element of arrays without seeing performance problems. You have to observe the array itself in order to handle adds and removes (assuming your arrays have this).
As far as I can tell, though, you have a selectedDictionary which is used to determine the other controls that are shown. In this case, you can use KVO to observe the value of selectedDictionary and when it changes, you can remove the observers from the previous selectedDictionary and add them to the keys in the current selectedDictionary. This is basically what bindings is doing in order to handle the display and setting, anyway.
One other consideration that I've used in the past is referenced in this StackOverflow post: NSMutableDictionary KVO. If you look at my answer here, I outline a trick for getting notifications when a new key is added or an existing key is deleted. It also has the benefit of giving you a notification when there's any change. It's not always a great solution, but it does save some effort on coding the list of keys to observe.
Beyond that, you'll have to add every key you're expecting to have an effect on the saved state of the document.