Question

new to the iOS SDK and Objective-C and just have a quick question regarding the NSTimeInterval.

I have a really simple game, and I want to show for how long the game have been played (so that I can save away a best time).

Now, of course if I set the label’s text with something like this:

NSTimeInterval elapsedTime = [startDate timeIntervalSinceNow];
theLabel.text = [NSString stringWithFormat:@"%.2f", -elapsedTime];

The text of the label will be how long time it will have passed since the game started, which is 0 seconds.

In what way can I have the elapsedTime object “running in the background” so that the player can se for how long he/she have played at all times?

Answer 1

Have a look as the NSTimer class to schedule a timer for a preset time and update the label in the callback.

-(void)viewDidLoad {
  [super viewDidLoad];

  // Add timer at 60 frames a second
  timer = [NSTimer scheduledTimerWithInterval:1.0/60.0 target:self selector:@selector(targetMethod:) userInfo:nil repeats: YES];  
}

-(void) targetMethod: NSTimer * theTimer {
... update label
}