Swift3でUIImageの回転

extensionでUIViewを拡張

extension UIView {
    func rotate360Degrees(duration: CFTimeInterval = 1.0, completionDelegate: AnyObject? = nil) {
        let rotateAnimation = CABasicAnimation(keyPath: "transform.rotation")
        rotateAnimation.fromValue = 0.0
        rotateAnimation.toValue = CGFloat(M_PI)
        rotateAnimation.duration = duration

        if let delegate: CAAnimationDelegate = completionDelegate as! CAAnimationDelegate? {
            rotateAnimation.delegate = delegate
        }
        self.layer.add(rotateAnimation, forKey: nil)
    }
}

どこかで呼び出し

self.YOUR_SUBVIEW.rotate360Degrees()

参考

Rotate a view for 360 degrees indefinitely in Swift?