Question

I have compiled the following code and there are no apparent runtime errors; however, the display freezes at 00:00:01 when I run it. It works if I only display the seconds attribute. Does anyone see an apparent oversight that I have missed in this code? I know there is a potential memory leak with the start button, but I will fix that eventually.

Thanks in advance.

#import "StopwatchViewController.h"

@implementation StopwatchViewController

- (IBAction)start{

    //creates and fires timer every second
    myTimer = [[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(showTime) userInfo:nil repeats:YES]retain];
}
- (IBAction)stop{
    [myTimer invalidate];
    myTimer = nil;
}

- (IBAction)reset{

    [myTimer invalidate];
    time.text = @"00:00:00";
}

(void)showTime{

    int currentTime = [time.text intValue];

    int new = currentTime +1;

    int secs  = new;
    int mins  = (secs/60) % 60;
    int hours = (mins/60);

    time.text = [NSString stringWithFormat:@"%.2d:%.2d:%.2d",hours, mins, secs];
}

Answer 1

You’re getting 0 from

int currentTime = [time.text intValue];

because the string that’s in text:

@"00:00:00"

can’t be converted to an int, so every time the timer fires, you add 1 to 0 and get 1, which you then display. The math would be inaccurate anyways, because minutes and seconds are “base-60″* — you’d need to do the reverse of the math you perform for separating hours/minutes/seconds, in order to get the total seconds again. You could just make currentTime an ivar, and keep the total number of seconds in it.

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*That’s not really what it’s called; I’m sure there’s a specific word for it.