Using a NSTimer for HH:MM:SS? - xcode

Question

How can I change this code so it has HH:MM:SS (hours, minutes, seconds)?
Do I need to add code in .h or .m so I known which one?
At the moment it goes up like 1, 2, 3, 4 etc.
Just to let you known I'm bait of a amateur would you copy and past so I known what you mean.
.h
#interface FirstViewController : UIViewController {
IBOutlet UILabel *time;
NSTimer *myticker;
//declare baseDate
NSDate* baseDate;
}
-(IBAction)stop;
-(IBAction)reset;
#end
.m
#import "FirstViewController.h"
#implementation FirstViewController
-(IBAction)start {
[myticker invalidate];
baseDate = [NSDate date];
myticker = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(showActivity) userInfo:nil repeats:YES];
}
-(IBAction)stop;{
[myticker invalidate];
myticker = nil;
}
-(IBAction)reset;{
time.text = #"00:00:00";
}
-(void)showActivity {
NSTimeInterval interval = [baseDate timeIntervalSinceNow];
NSUInteger seconds = ABS((int)interval);
NSUInteger minutes = seconds/60;
NSUInteger hours = minutes/60;
time.text = [NSString stringWithFormat:#"%02d:%02d:%02d", hours, minutes%60, seconds%60];
}

Answer 1

First, declare baseDate variable in your FirstViewController.h, like this:
#interface FirstViewController : UIViewController {
IBOutlet UILabel *time;
NSTimer *myticker;
//declare baseDate
NSDate* baseDate;
}
Then, in the FirstViewController.m start method add baseDate = [NSDate date] like this:
-(IBAction)start {
[myticker invalidate];
baseDate = [NSDate date];
myticker = [NSTimer scheduledTimerWithTimeInterval:.01 target:self selector:#selector(showActivity) userInfo:nil repeats:YES];
}
After that, change your showActivity method to look like this:
-(void)showActivity {
NSTimeInterval interval = [baseDate timeIntervalSinceNow];
double intpart;
double fractional = modf(interval, &intpart);
NSUInteger hundredth = ABS((int)(fractional*100));
NSUInteger seconds = ABS((int)interval);
NSUInteger minutes = seconds/60;
NSUInteger hours = minutes/60;
time.text = [NSString stringWithFormat:#"%02d:%02d:%02d:%02d", hours, minutes%60, seconds%60, hundredth];
}
Also note, that you will have to change the interval value for your timer, otherwise your label will only be updated once a second.