Objective C 到 Swift 的转换（协议）答案

【问题标题】：Objective C to Swift Conversion (Protocol)Objective C 到 Swift 的转换（协议）
【发布时间】：2016-01-22 14:18:35
【问题描述】：

我正在尝试将下面的代码转换为 swift

- (id <UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                   animationControllerForOperation:(UINavigationControllerOperation)operation
                                                fromViewController:(UIViewController *)fromVC
                                                  toViewController:(UIViewController *)toVC
{
    // minimum implementation for example
    RMPZoomTransitionAnimator *animator = [[RMPZoomTransitionAnimator alloc] init];
    animator.goingForward = (operation == UINavigationControllerOperationPush);
    animator.sourceTransition = (id<RMPZoomTransitionAnimating>)fromVC;
    animator.destinationTransition = (id<RMPZoomTransitionAnimating>)toVC;
    return animator;
}

到目前为止我已经成功转换，但我想知道我应该如何转换这个(id<RMPZoomTransitionAnimating>)fromVC

func navigationController(navigationController: UINavigationController, animationControllerForOperation operation: UINavigationControllerOperation, fromViewController fromVC: UIViewController, toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    let animator: RMPZoomTransitionAnimator = RMPZoomTransitionAnimator();

    animator.goingForward = (operation == UINavigationControllerOperation.Push);
    animator.sourceTransition = fromVC as! RMPZoomTransitionAnimating;//DOESN'T COMPILE
    animator.destinationTransition = toVC as! RMPZoomTransitionAnimating;//DOESN'T COMPILE
    return animator;
}

我不知道那叫什么。知道那是什么吗？我试着投它，但它不起作用

【问题讨论】：

标签： ios objective-c swift uinavigationcontroller

【解决方案1】：

RMPZoomTransitionAnimator swift3.0 扩展

extension ViewController: UINavigationControllerDelegate {

func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationControllerOperation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    if fromVC is RMPZoomTransitionAnimating && toVC is RMPZoomTransitionAnimating {
        let animator = RMPZoomTransitionAnimator()
        animator.goingForward = (operation == .push)
        animator.sourceTransition = fromVC as? RMPZoomTransitionAnimating & RMPZoomTransitionDelegate
        animator.destinationTransition = toVC as? RMPZoomTransitionAnimating & RMPZoomTransitionDelegate
        return animator
    } else {
        return nil
    }
  }
}

extension ViewController: RMPZoomTransitionAnimating, RMPZoomTransitionDelegate {

func imageViewFrame() -> CGRect {
    if let collectionView = self.collectionView(),
        let indexPath = self.selectedIndexPath,
        let cell = collectionView.cellForItemAtIndexPath(indexPath) as? NewsCollectionViewCell,
        let imageView = cell.fgImageView {
        let frame = imageView.convertRect(imageView.frame, toView: self.view.window)
        return frame
    }

    return CGRect.zero
}

func transitionSourceImageView() -> UIImageView! {
    let imageView = UIImageView()
    imageView.clipsToBounds = true
    imageView.isUserInteractionEnabled = false
    imageView.contentMode = .scaleAspectFill
    imageView.frame = imageViewFrame()
    imageView.image = self.selectedViewCell?.fgImageView!.image
    return imageView
}

func transitionSourceBackgroundColor() -> UIColor! {
    return UIColor.white
}

func transitionDestinationImageViewFrame() -> CGRect {
    return imageViewFrame()
}

func zoomTransitionAnimator(_ animator: RMPZoomTransitionAnimator!, didCompleteTransition didComplete: Bool, animatingSourceImageView imageView: UIImageView!) {

}
}

【讨论】：

【解决方案2】：

你可以按如下方式投射：

animator.sourceTransition = fromVC as? protocol<RMPZoomTransitionAnimating, RMPZoomTransitionDelegate>

只有当fromVC同时符合RMPZoomTransitionAnimating和RMPZoomTransitionDelegate这两个协议时，转换才会成功

P/S：在编写 Swift 代码时，你应该忘记semi-colon

【讨论】：