How to get an update NSUserDefault on iOS 4?

Question

I am developing an iPhone application, I encounter a problem on the iOS4 because of multi task.

This application has the default settings defined in a Settings.bundle. If I run my application then I left it (so it goes in the background). I'll change the settings and restarts the application (it comes out of standby and method: applicationDidBecomeActive () is called).

Values in NSUserDefault are not updates, but when I leave the application and relaunch. The values are good.

Does someone experience the same problem as me? Is what I'm doing something wrong?

Thank you for your advice / help.

Answer 1

I had the same problem as you, and got around it by calling

[[NSUserDefaults standardUserDefaults] synchronize];

in applicationDidBecomeActive.

For some reason the [NSUserDefaults standardUserDefaults] object you can access in your app isn't synchronized with the actual plist files backing it when an app becomes active again after having been suspended. Calling the synchronize method forces a synchronization.

Answer 2

You need to listen for settings changes. Best way to do it is to set up a listener wherever you need it:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(settingsChanged) name:NSUserDefaultsDidChangeNotification object:nil];

The only thing you need to make sure of is that you don't change any settings in your listener, or you get infinite recursion without a little more logic being added in.

I'd stay away from synchronizing because in my experience I found I had to run it twice. But that's accidental behavior. A listener will notify you when the new settings have been re-read from the store.