NSUserDefaults default value returning (null)?

问题

This is probably something really simple that I am missing, why when using the code below to access settings does the default value return as (null)

- (void)updateUIForDistanceUnits {
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    NSString *test = [userDefaults stringForKey:@"IDDistance"];
    NSLog(@"DISTANCE: %@", test);
}

Root.plist

回答1:

The default value in Root.plist is just what the UI shows if there's no value set, and you have to do the same in your code or set up [NSUserDefaults -registerDefaults] correctly in your application.

You should find that once you set the value in Settings.app NSUserDefaults will return the correct value.

来源：https://stackoverflow.com/questions/10706685/nsuserdefaults-default-value-returning-null