Timers in cocoa

// This sample creates a repeating timer and updates a label on the view each time the timer executes

@interface TimerTextViewController : UIViewController {

	IBOutlet UILabel *label;
	
	NSTimer *repeatingTimer;
	
	NSUInteger timerCount;
}

@property (nonatomic, retain) NSTimer *repeatingTimer;

-(IBAction)startTimer:(id)sender;

-(IBAction)stopTimer:(id)sender;

-(void)targetMethod:(NSTimer*)theTimer;

@end

@implementation TimerTextViewController

@synthesize repeatingTimer;

-(IBAction)startTimer:(id)sender{
	timerCount = 1;
	
    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.0 //interval in seconds
		       target:self //this is the object that owns the method to execute
                       selector:@selector(targetMethod:) //this is the method that gets called when the timer ticks, it can be named anything but its signature is important (see below)
                       userInfo:nil 
                       repeats:YES];
	
    self.repeatingTimer = timer;
	
}

// the invalidate method stops the timer
-(IBAction)stopTimer:(id)sender{
	[repeatingTimer invalidate];
}

//this method could be called anything, but it needs this signature
- (void)targetMethod:(NSTimer*)theTimer {
	NSString *countString = [NSString stringWithFormat:@"%lu", timerCount];
	[label setText:countString];
	timerCount++;
}
@end