Setting up implementation for cityButtonTapped: method in "Build a World Clock in Objective-C."

ViewController.m

@implementation ViewController
   - (void)viewDidLoad {
        [super viewDidLoad];
   }

   - (IBAction)cityButtonTapped:(UIButton *)sender { //Gets which button is tapped
         switch (sender.tag) {
            case 100:
               self.timeZone = @"EST";
               self.selectedButton = self.nyc;
               break;

            case 101:
               self.timeZone = @"CEST";
               self.selectedButton = self.paris;
               break;

            case 102:
               self.timeZone = @"MSD";
               self.selectedButton = self.moscow;
               break;

            case 103:
               self.timeZone = @"HKT";
               self.selectedButton = self.hongKong;
               break;

            case 104:
               self.timeZone = @"HST";
               self.selectedButton = self.honolulu;
               break;

            case 105:
               self.timeZone = @"PST";
               self.selectedButton = self.seattle;
               break;

            default:
               self.timeZone = @"EST";
               self.selectedButton = self.nyc;
               break;
      }
      [self setTappedCityTimer];
   }
@end