[wataru]

I've got an application that's designed as follows:

AppController is a subclass of NSObject that deals with the main interface,
PrefsController is also a subclass of NSObject that deals with the preferences window and maintains arrays of persistent custom objects that both Controllers need to access.
Both Controllers have instance variables pointing to each other.

Right now, I have it set up so that when AppController needs to get a list of, say, configured "gizmos," it uses [prefsController gizmos] to get it. When it has modified a gizmo and the changes need to be saved to disk, it does [prefsController saveGizmos], which tells PrefsController to put the gizmo array into NSSharedUserDefaults and synchronize the defaults, etc.

This seems odd and inefficient for some reason. Since both Controllers need access to the same set of objects, it seems like it would make more sense to have them both read from a shared store like NSSharedUserDefaults. But then changes in one aren't reflected in changes in the other for some reason, and the two sets are constantly out of sync, and they could easily overwrite each other's changes if I have them save to UserDefaults separately. So what is the best practice in this case?

Also, I'm wondering if it would be better to do something like having PrefsController listen for a GizmosHaveChanged notification, instead of being told directly to saveGizmos. When is it better to use indirect communication like NSNotifications instead of direct messaging?

[techtrucker]

I can't say what the ramifications are of my method, but in a somewhat similar situation I used notifications. Perhaps there's something technically "wrong" with doing it that way but it works exactly how I want it to.

[bewebste]

What I usually do is to have a separate Preferences object that has accessors that pass values to/from NSUserDefaults with setters that send out notifications that any relevant controllers can listen to. Then I just have a shared instance of Preferences that any object can get/set its values from. This setup also keeps with the MVC paradigm better than storing values right in the prefs controller.

[wataru]

How do you make shared instances of things? I assume you mean shared as in something along the lines of [NSUserDefaultsController sharedUserDefaultsController], right?

Also, one reason I asked this question is because I'm thinking about moving control of the gizmo array to AppController instead of PrefsController. This doesn't make a lot of logical sense, but as things are:
1. The PrefsController is instantiated by the AppController upon init
2. The PrefsController loads the Preferences.nib for the window it controls during init or else the app crashes with a SIGSEV

I can't figure out why the app crashes unless I load the Preferences.nib. I'd like to delay loading the nib until the user explicitly opens the prefs window, but right now the only way to do that is to delay loading the PrefsController. But that means that AppController doesn't have access to the gizmos list.

I'm kind of rambling here, but do people understand what I'm getting at?