Having milliseconds in my timer in Objective-C - objective-c

Question

I'm doing a stopwatch using a youtube tutorial. The problem is that I want milliseconds in my timer but the tutorial only shows how to get seconds and minutes. I would like to get the milliseconds displayed like the minutes and seconds, but I've got no idea how to do it.
How to get milliseconds using this code?
#implementation ViewController {
bool start;
NSTimeInterval time;
}
- (void)viewDidLoad {
[super viewDidLoad];
self.display.text = #"0:00";
start = false;
}
- (void) update {
if ( start == false ) {
return;
}
NSTimeInterval currentTime = [NSDate timeIntervalSinceReferenceDate];
NSTimeInterval elapsedTime = currentTime - time;
int minutes = (int) (elapsedTime / 60.0);
int seconds = (int) (elapsedTime = elapsedTime - (minutes * 60));
self.display.text = [NSString stringWithFormat:#"%u:%02u", minutes, seconds];
[self performSelector:#selector(update) withObject:self afterDelay:0.1];
}

Answer 1

According to the docs, "NSTimeInterval is always specified in seconds; it yields sub-millisecond precision over a range of 10,000 years." So all you need to do is extract the milliseconds from your elapsedTime variable and then format your text again so that it includes milliseconds. It might looks something like this:
NSInteger time = (NSInteger)elapsedTime;
NSInteger milliseconds = (NSInteger)((elapsedTime % 1) * 1000);
NSInteger seconds = time % 60;
NSInteger minutes = (time / 60) % 60;
//if you wanted hours, you could do that as well
//NSInteger hours = (time / 3600);
self.display.text = [NSString stringWithFormat: "%ld:%ld.%ld", (long)minutes, (long)seconds, (long)milliseconds];