Translating a UIView and setting the label text - ios

Question

I'm starting to learn iOS gesture recognizers, going through this tutorial http://www.appcoda.com/ios-gesture-recognizers/. Have a problem translating a view with UIPanGestureRecognizer while setting the UILabels' text to the gesture's velocity.
I have been successfully translating a view with a pan gesture like this (with the help of IB):
PanViewController.h
#interface PanViewController : UIViewController
#property (weak, nonatomic) IBOutlet UIView *testView;
#property (weak, nonatomic) IBOutlet UILabel *horizontalVelocityLabel;
#property (weak, nonatomic) IBOutlet UILabel *verticalVelocityLabel;
#end
PanViewController.m
#interface PanViewController ()
- (void)moveViewWithGestureRecognizer:(UIPanGestureRecognizer *)panGestureRecognizer;
#end
#implementation PanViewController
- (void)viewDidLoad {
[super viewDidLoad];
UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(moveViewWithGestureRecognizer:)];
[self.testView addGestureRecognizer:panGestureRecognizer];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
- (void)moveViewWithGestureRecognizer:(UIPanGestureRecognizer *)panGestureRecognizer {
CGPoint touchLocation = [panGestureRecognizer locationInView:self.view];
self.testView.center = touchLocation;
}
But when I add the following lines to this method, the view stops translating, but the UILabels get updated with the velocity:
CGPoint velocity = [panGestureRecognizer velocityInView:self.view];
self.horizontalVelocityLabel.text = [NSString stringWithFormat:#"Horizontal Velocity: %.2f points/sec", velocity.x];
self.verticalVelocityLabel.text = [NSString stringWithFormat:#"Vertical Velocity: %.2f points/sec", velocity.y];
I'd like to understand what i'm doing wrong. How can I fix it?
Thanks in advance.