resume function does not work correctly in NSTime - ios

Question

I have a NSTimer that functions as a stopwatch. It makes the time count and has the pause function that works properly but the function does not work continue. The timer seems to be counting even paused but not updated the label and when I touch the button comes down to is to continue from where you left it continues counting that did not stop. How can I fix this?
this is my chronometer code:
- (void)viewDidLoad {
[super viewDidLoad];
[self setUp];
self.isPaused = NO;
}
- (void) setUp {
startDate = [NSDate date];
_timer = [NSTimer scheduledTimerWithTimeInterval: 1.0/100.0 target: self selector: #selector(timerUpdating) userInfo: nil repeats: true];
}
-(void)timerUpdating {
NSDate *currentDate = [NSDate date];
NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate];
NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval];
NSDateFormatter *dateFormater = [[NSDateFormatter alloc]init];
[dateFormater setDateFormat:#"mm:ss"];
[dateFormater setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
NSString *timeString = [dateFormater stringFromDate:timerDate];
if (self.isPaused == NO){
_timerLabel.text = timeString;
}
}
- (IBAction)pauseAction:(id)sender {
[self pauseTimer:self.timer];
}
- (IBAction)resumeAction:(id)sender {
[self resumeTimer:self.timer];
}
-(void) pauseTimer:(NSTimer *)timer {
self.isPaused = YES;
self.pauseStart = [NSDate date];
self.previousFireDate = [timer fireDate];
[timer setFireDate:[NSDate distantFuture]];
}
-(void) resumeTimer:(NSTimer *)timer {
self.isPaused = NO;
NSDate *currentDate = [NSDate date];
NSTimeInterval pauseTime = [currentDate timeIntervalSinceDate:pauseStart];
NSDate *neededFireDate = [NSDate dateWithTimeInterval:pauseTime sinceDate:previousFireDate];
[timer setFireDate:neededFireDate];
NSLog(#"Fire Date: %#", timer.fireDate);
}

Answer 1

At timerUpdating you set NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate];. This will not take into account if the user paused the timer or not.
To correct this behavior you could do something like:
In .h (set a member variable):
NSTimeInterval pausedTime;
In .m (3 lines edited)
- (void)viewDidLoad {
[super viewDidLoad];
[self setUp];
self.isPaused = NO;
pausedTime = 0; //edit
}
- (void) setUp {
startDate = [NSDate date];
_timer = [NSTimer scheduledTimerWithTimeInterval: 1.0/100.0 target: self selector: #selector(timerUpdating) userInfo: nil repeats: true];
}
-(void)timerUpdating {
NSDate *currentDate = [NSDate date];
NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate] - pauseTime;//edit
NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval];
NSDateFormatter *dateFormater = [[NSDateFormatter alloc]init];
[dateFormater setDateFormat:#"mm:ss"];
[dateFormater setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
NSString *timeString = [dateFormater stringFromDate:timerDate];
if (self.isPaused == NO){
_timerLabel.text = timeString;
}
}
- (IBAction)pauseAction:(id)sender {
[self pauseTimer:self.timer];
}
- (IBAction)resumeAction:(id)sender {
[self resumeTimer:self.timer];
}
-(void) pauseTimer:(NSTimer *)timer {
self.isPaused = YES;
self.pauseStart = [NSDate date];
self.previousFireDate = [timer fireDate];
[timer setFireDate:[NSDate distantFuture]];
}
-(void) resumeTimer:(NSTimer *)timer {
self.isPaused = NO;
NSDate *currentDate = [NSDate date];
NSTimeInterval pauseTime = [currentDate timeIntervalSinceDate:pauseStart];
pausedTime += pauseTime;//edit
NSDate *neededFireDate = [NSDate dateWithTimeInterval:pauseTime sinceDate:previousFireDate];
[timer setFireDate:neededFireDate];
NSLog(#"Fire Date: %#", timer.fireDate);
}