[iOS] 画像をフェードアニメーションで切り替えていく

class SampleViewController: UIViewController {

    @IBOutlet weak var imageView: UIImageView!
    var images: [UIImage] = [
        UIImage(named: "sample_img1"),
        UIImage(named: "sample_img2"),
        UIImage(named: "sample_img3")
    ]
    let index = 0
    let animationDuration: TimeInterval = 1
    let switchingInterval: TimeInterval = 3

    override func viewDidLoad() {
        super.viewDidLoad()
        imageView.image = images[index]
        animateImageView()
    }

    // 画像をフェードで切り替えるアニメーション
    func animateImageView() {
        CATransaction.begin()
        CATransaction.setAnimationDuration(animationDuration)
        CATransaction.setCompletionBlock {
            DispatchQueue.main.asyncAfter(deadline: .now() + self.switchingInterval) {
                self.animateImageView()
            }
        }

        let transition = CATransition()
        transition.type = kCATransitionFade

        brandImageImageView.layer.add(transition, forKey: kCATransition)
        brandImageImageView.image = brandImages[nextBrandImagesIndex]

        CATransaction.commit()

        nextBrandImagesIndex = nextBrandImagesIndex < brandImages.count - 1 ? nextBrandImagesIndex + 1 : 0
    }
}

参考: stackoverflow「Adding Image Transition Animation in Swift」