Question

I use NSUserDefaults in my setting. App works well even I press home key let app into background, but if I kill the app, the data save in NSUserDefaults will lost. Here is my code. I have use synchronize.
The First initialize:

 if (![userDefaults integerForKey:
          kORFootageAirPlayModeKey])
    {
        [userDefaults setInteger:TRUE forKey:kORFootageAirPlayModeKey];
    }
    [userDefaults synchronize];

Read value out in a viewController:

airPlayMode = [[NSUserDefaults standardUserDefaults]integerForKey:kORFootageAirPlayModeKey];

Set it in a action:

- (IBAction)changeAirPlayStatus:(id)sender
{

    if (sender)
    {
        airPlayMode = [sender tag];

        [[NSUserDefaults standardUserDefaults] setInteger:airPlayMode forKey:kORFootageAirPlayModeKey];
        [[NSUserDefaults standardUserDefaults] synchronize];
    }
.....

}

Answer 1

I don’t see a reason for that.

Have you checked in the Simulator directory, under Library/Caches there’s the plist that saves your NSUserDefaults. Check if it’s written correctly.

And please, don’t use setInteger:TRUE. This is wrong on so many levels. Use setBOOL:YES instead. Or setInteger:1.