Why is NSUserDefaults not saving my values?

Hi I am trying to use NSUserDefaults to save some default values in database. I am able to save the values in the NSUserDefaults (even check开发者_如何学编程ed it in NSLog). Now I need the values in app delegate when the application is restarted. But I am not getting anything in the NSUserDefaults. Following is my code from my class where I save the values in NSUserDefaults:

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];

            [prefs setObject:appDel.dictProfile forKey:@"dict"];
            NSLog(@"%@",[prefs valueForKey:@"dict"]);

Following is my code from App Delegagte:

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];

NSLog(@"%@",[prefs valueForKey:@"dict"]);

the above code always returns me null. Can some one please help me?

If you terminate your app by pressing the home button (in the Simulator or on the device), your NSUserDefaults will get saved.

If you terminate your app by pressing "Stop" in Xcode (in the Simulator or on the device), your NSUserDefaults might get saved, but there's a good chance they won't. NSUserDefaults persists any changes periodically, and if you terminate the process before they've been persisted, they'll be gone. You can force the save by calling:

[[NSUserDefaults standardUserDefaults] synchronize];

Addendum:

In iOS4 (this answer was originally written when iOS3 was the public release), your NSUserDefaults may not get saved when pressing the home button. Manually calling [[NSUserDefaults standardUserDefaults] synchronize] in applicationDidEnterBackground: should ensure that your NSUserDefaults are saved correctly (this should really be a built-in behaviour IMO).

This code works fine for me .

NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];

if (standardUserDefaults) {
    [standardUserDefaults setObject:myString forKey:@"Prefs"];
    [standardUserDefaults synchronize];
}

You didn't say whether you are running on a device or in the simulator, but if you restart the application in the simulator, all preferences will be reset between launches if you launch from Xcode. The preferences will only be preserved if you relaunch from the simulator itself.

In my case I was saving and retrieving a string. When I synchronized after saving and then retrived in another thread, it was not working properly. The problem was solved by synchronizing both after saving and before retreiving.