class RotationViewController: UIViewController {

? ? @IBOutlet weak var wheel: UIImageView!

? ? override func viewDidLoad() {

? ? ? ? super.viewDidLoad()

? ? ? ? // Do any additional setup after loading the view.

? ? }

? ? override func didReceiveMemoryWarning() {

? ? ? ? super.didReceiveMemoryWarning()

? ? ? ? // Dispose of any resources that can be recreated.

? ? }

?? ?

? ? override func viewDidAppear(animated: Bool) {

? ? ? ? super.viewDidAppear(animated)

? ? ? ? UIView.animateWithDuration(1, animations: {

? ? ? ? self.wheel.transform = CGAffineTransformMakeRotation(<#CGFloat#>(M_PI))

? ? ? ? })

? ? }

?? ?

}

求解答？？？謝謝了。