CountDown Timer in iPhone SDK

This code is used to create a countdown timer in iPhone app.

1. Code for .h file.

@interface UIMyContoller : UIViewController {

    NSTimer *timer;
    IBOutlet UILabel *myCounterLabel;
}

@property (nonatomic, retain) UILabel *myCounterLabel;
-(void)updateCounter:(NSTimer *)theTimer;
-(void)countdownTimer;

@end

2. Code for .m file.

@implementation UIMyController
@synthesize myCounterLabel;

int hours, minutes, seconds;
int secondsLeft;

- (void)viewDidLoad {
    [super viewDidLoad];
    
    secondsLeft = 16925;
    [self countdownTimer];
}

- (void)updateCounter:(NSTimer *)theTimer {
    if(secondsLeft > 0 ){
        secondsLeft -- ;
        hours = secondsLeft / 3600;
        minutes = (secondsLeft % 3600) / 60;
        seconds = (secondsLeft %3600) % 60;
        myCounterLabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hours, minutes, seconds];
    }
    else{
        secondsLeft = 16925;
    }
}

-(void)countdownTimer{
    
    secondsLeft = hours = minutes = seconds = 0;
    if([timer isValid])
    {
        [timer release];
    }
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];  
    timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(updateCounter:) userInfo:nil repeats:YES];
    [pool release];
}