can't open view controller

I ran my game. When I wanna go to the game store view controller in simulator, the app crashes. See the code:

.h

@property (weak, nonatomic) IBOutlet UILabel *coinLabel;
@property (weak, nonatomic) IBOutlet UILabel *itemLabel;

.m

int coin;
int itemQty;

- (IBAction)buy:(id)sender {
    coin = coin - 50;
    itemQty = itemQty + 1;
}
- (void)viewDidLoad {
    [super viewDidLoad];
    UILabel* itemLabel = [[UILabel alloc] init];
    itemLabel.text = [NSString stringWithFormat:@"%d", itemQty];

    UILabel* coinLabel = [[UILabel alloc] init];
    coinLabel.text = [NSString stringWithFormat:@"%d", coin];
}

... //I didn't edit anything here

Please help. Thanks