Timer count throughout the game in Objective c - ios

Question

I am creating a game application in which I need to set timer of 2 minutes throughout the app screens in objective c.
I am creating it in viewDidLoad but it is creating a new instance every-time the view loads.
Here is the code which I am using :
#interface SomeViewController ()
{
int timerCounter;
NSTimer *timer;
}
#property (strong, nonatomic) IBOutlet UILabel *timerLbl;
#end
#implementation SomeViewController
- (void)viewDidLoad {
[super viewDidLoad];
[self startCountdown];
}
- (void)startCountdown
{
timer = [NSTimer scheduledTimerWithTimeInterval:1
target:self
selector:#selector(countdownTimer:)
userInfo:nil
repeats:YES];
}
- (void)countdownTimer:(NSTimer *)timer
{
timerCounter--;
int minutes = timerCounter / 60;
int seconds = timerCounter % 60;
NSString *string = [NSString stringWithFormat:#"%02d", minutes];
NSString *string2 = [NSString stringWithFormat:#"%02d", seconds];
NSString *timeTotal = [string stringByAppendingString:#":"];
NSString *timeTotal2 = [timeTotal stringByAppendingString:string2];
_timerLbl.text = timeTotal2;
if (timerCounter <= 0) {
[timer invalidate];
}
}

Answer 1

You need to invalidate it whenever the VC deallocates
- (void)dealloc {
[timer invalidate];
}
//
The second VC may look like this
#import "ggViewController.h"
NSInteger timerCounter = 120; // declared global to hold the value
#interface ggViewController ()
{
NSTimer*timer;
}
#end
#implementation ggViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
// instead of using selector use this inline callback
timer = [NSTimer scheduledTimerWithTimeInterval:1.0 repeats:true block:^(NSTimer * timer) {
timerCounter--;
int minutes = timerCounter / 60;
int seconds = timerCounter % 60;
NSString *string = [NSString stringWithFormat:#"%02d", minutes];
NSString *string2 = [NSString stringWithFormat:#"%02d", seconds];
NSString *timeTotal = [string stringByAppendingString:#":"];
NSString *timeTotal2 = [timeTotal stringByAppendingString:string2];
_timerLbl.text = timeTotal2;
if (timerCounter <= 0) {
[timer invalidate];
}
}];
}
-(void)viewDidDisappear:(BOOL)animated{
[super viewDidDisappear:animated];
[timer invalidate];
}
- (IBAction)gg:(id)sender {
[self dismissViewControllerAnimated:true completion:nil];
}
#end