Question

I set up multiple NSUserDefaults in my app that work for the most part. The NSUserDefaults are called from one ViewController and implemented at another (such as in a game with a level select). This seems to work well, until the user presses the back button on the level select screen. When they try to go back to the level select viewController, the NSUserDefaults are not loaded onto the screen.
Here is my code:

LevelSelectViewController:

- (void)viewDidLoad
{       
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    [userDefaults synchronize];

    [super viewDidLoad];
}

- (void)Level1DidFinish:(Level1 *)controller
{
    [self dismissModalViewControllerAnimated:YES];

    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    NSInteger rank = [userDefaults integerForKey:@"levelRank"];
    {
        if (rank == 1) {
            button2.hidden = NO;

        }
    }
}

Level1ViewController:

{            
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    [userDefaults setInteger:1 forKey:@"levelRank"];
}

Answer 1

Your first issue is you are creating an instance of userDefaults, but are not setting any values. So calling synchronize here is actually doing nothing:

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
[userDefaults synchronize];

After you set a your Integer, then you need to call synchronize:

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
[userDefaults setInteger:1 forKey:@"easyRank"];
[userDefaults synchronize];