title: Reset NSTimer after navigating to another view
body: <p>Currently I am developing a game which needs a stop watch say 1 minute,when user taps the play button it enters the game screen,I want the to run the stop watch count down of 1 minute 01:00,00:59,00:58 etc. For that reason I searched and found NSTimer would be the ideal choice to implement a stop watch.Hence I took a label,created an instance of NSTimer,assigned time interval and started decrementing the value in timer label,i.e.:</p>
  
  <pre><code>-(void)viewDidAppear:(BOOL)animated
  {
      self.stopWatchTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(viewWillAppear:) userInfo:nil repeats:YES];
      [super viewDidAppear:YES];
  }
  
  -(void)viewWillAppear:(BOOL)animated
  {
      static int currentTime = 60;
      int newTime = currentTime--;
      int minutesRemaining = newTime / 60; // integer division, truncates fractional part
      int secondsRemaining = newTime % 60; // modulo division
  
      self.timerLabel.text = [NSString stringWithFormat:@"%02d:%02d", minutesRemaining, secondsRemaining];
  
      if ([self.timerLabel.text isEqualToString:@"00:00"])
      {
          [stopWatchTimer invalidate];
      }
      [super viewWillAppear:YES];
  }
  </code></pre>
  
  <p>The problem here is the timer starts running 01:00,00:59,00:58 and goes on,say at 53rd second,I navigated to another view and came back,it is running from 00:53,00:52 and so on,but I want it to run from 01:00 and for that I implemented invalidating NSTimer in viewDidDisappear i.e.</p>
  
  <pre><code>-(void)viewDidDisappear:(BOOL)animated
  {
      if ([stopWatchTimer isValid])
      {
          [stopWatchTimer invalidate];
          self.stopWatchTimer = nil;
      }
      [super viewDidDisappear:YES];
  }
  </code></pre>
  
  <p>Still the same issue exists!</p>
  
  <p>Done lots of Research on the issue and found no answer useful and working.</p>
  
  <p>Can some one please guide me,any help is appreciated.</p>
  
  <p>Thanks every one in advance :)</p>