Question

Once a IBAction is pressed, I want a counter which counts up.

But in this form

00:00:00
Hours:minutes:seconds

This is the code so far:

-(void)countUp {

    mainInt += 1;
    seconds.text = [NSString stringWithFormat:@"%02d", mainInt];

}

This only counts up in 00 format

Thanks for the help!

Answer 1

Just do the appropriate math to break the count up into its constituent parts:

NSString *timeString = [NSString stringWithFormat:@"%02d:%02d:%02d",
                                                  totalSeconds/3600,        // hours
                                                  (totalSeconds/60)%60,     // minutes
                                                  totalSeconds%3600]        // seconds

For the sake of readability, it’d be nice to replace that inline math with macros or functions, for example:

#define secondsPerMinute 60
#define minutesPerHour 60

int hours(int secs) {
    return secs/(minutesPerHour * secondsPerMinute);
}

int minutes(int secs) {
    return (secs/secondsPerMinute) % minutesPerHour;
}

int seconds(int secs) {
    return secs % (minutesPerHour * secondsPerMinute);
}

// ...
NSString *timeString = [NSString stringWithFormat:@"%02d:%02d:%02d",
                                                  hours(totalSeconds),
                                                  minutes(totalSeconds),
                                                  seconds(totalSeconds)];

Often when implementing this sort of display, you don’t want the colons to jump around as the elapsed time changes. Many fonts have fixed-width numerals, so it’s not always a problem, but you might want to use three separate labels for the hours, minutes, and seconds, with unchanging labels in between for the colons.

Another approach to the math above is to store the seconds, minutes, and hours in three variables instead of one, and just be careful to increment minutes and reset seconds when seconds hit 60, and so on. To make this easier to use, encapsulate it in a class, like:

@interface Time : NSObject {
    int seconds;
    int minutes;
    int hours;
}
- (void)countUp;
- (NSString*)timeString;
@end;