设置点击手势出现了错误

我创建了一个标签，然后在上面设置的点击，但是点击之后报错

.h文件：

@interface ViewController : UIViewController
{
    UILabel *alabel;
}
@property (strong, nonatomic) UILabel *alabel;

.m文件：

- (void)viewDidLoad
{
    [super viewDidLoad];

    alabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 10, 100, 50)];
    alabel.text = @"Drag me!";

    alabel.userInteractionEnabled = YES;

    UITapGestureRecognizer *tapGesture =[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(labelTap)];
    [alabel addGestureRecognizer:tapGesture];

    [self.view addSubview:alabel];
}

- (void)labelTap:(UITapGestureRecognizer *)tapGesture {
    TouchLabelViewController *touchLabelViewController = [[TouchLabelViewController alloc] initWithNibName:@"TouchLabelViewController" bundle:[NSBundle mainBundle]];
    [self presentModalViewController:touchLabelViewController animated:NO];
    }

日志显示：

2012-10-29 11:19:17.313 DragableControll[795:f803] -[ViewController labelTap]: unrecognized selector sent to instance 0x68956b0
2012-10-29 11:19:17.316 DragableControll[795:f803] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[ViewController labelTap]: unrecognized selector sent to instance 0x68956b0'