How to Rotate UIButton by tap and hold (hold - rotate by finger)

I'm noob in ios development. I need some help. I have custom UIButton with picture "arrow", so I need to rotate this button by pressing and moving finger in +360 gr. and -360 gr., like compass arrow.

Here is code that makes rotation.

-(void)LongPress:(UILongPressGestureRecognizer *)gesture {

    CGPoint p = [gesture locationInView:self.view];

    CGPoint zero;
    zero.x = self.view.bounds.size.width / 2.0;
    zero.y = self.view.bounds.size.height / 2.0;

    CGPoint newPoint;

    newPoint.x = p.x - zero.x;
    newPoint.y = zero.y - p.y;
    CGFloat angle;
    angle = atan2(newPoint.x, newPoint.y);
    self.myButton.transform = CGAffineTransformRotate(CGAffineTransformIdentity, angle);

}