NSTimer Decrease the time by seconds/milliseconds - iphone

Question

I am developing a QuiZ app. It needs a countdown timer, In that I want to start a timer at 75:00.00 (mm:ss.SS) and decrease it to 00:00.00 (mm:ss.SS) by reducing 1 millisecond. I want to display an alert that Time UP! when time reaches to 00:00.00 (mm:ss.SS).
I am displaying the time by following below link
Stopwatch using NSTimer incorrectly includes paused time in display

Answer 1

Here is a simple solutions to your problem.
Declarations
#interface ViewController : UIViewController
{
IBOutlet UILabel * result;
NSTimer * timer;
int currentTime;
}
- (void)populateLabelwithTime:(int)milliseconds;
-(IBAction)start;
-(IBAction)pause;
#end
Definition
- (void)viewDidLoad
{
[super viewDidLoad];
currentTime = 270000000; // Since 75 hours = 270000000 milli seconds
}
-(IBAction)start{
timer = [NSTimer scheduledTimerWithTimeInterval:.01 target:self selector:#selector(updateTimer:) userInfo:nil repeats:YES];
}
-(IBAction)pause{
[timer invalidate];
}
- (void)updateTimer:(NSTimer *)timer {
currentTime -= 10 ;
[self populateLabelwithTime:currentTime];
}
- (void)populateLabelwithTime:(int)milliseconds {
int seconds = milliseconds/1000;
int minutes = seconds / 60;
int hours = minutes / 60;
seconds -= minutes * 60;
minutes -= hours * 60;
NSString * result1 = [NSString stringWithFormat:#"%#%02dh:%02dm:%02ds:%02dms", (milliseconds<0?#"-":#""), hours, minutes, seconds,milliseconds%1000];
result.text = result1;
}

Answer 2

Use following code for reducing timer.
double dblRemainingTime=60; //1 minute
if(dblRemainingTime >0)
{
dblRemainingTime -= 1;
int hours,minutes, seconds;
hours = dblRemainingTime / 3600;
minutes = (dblRemainingTime - (hours*3600)) / 60;
seconds = fmod(dblRemainingTime, 60);
[lblRemainingTime setText:[NSString stringWithFormat:#"%02d:%02d",minutes, seconds]];
}
else
alert('Time up buddy');