ios - 快速更改其他类中的字符串(不使其成为全局字符串)

Question

我想修改另一个类中的string。然后，此类将在函数中使用该变量。

这是我到目前为止尝试过的方法。展开它时我总是遇到错误: fatal error :在展开可选值时意外发现 nil。有谁知道如何更改 urlString(最好不要将其设为全局)？我找不到 swift 的解决方案，它也涉及 stackoverflow 上的函数...如果您认为我将必须使其成为全局性的，请告诉我!

在类#1

let videoUrl =  "https:...sometestvideo.mov"
videoPlayerView.urlString = videoUrl

在类#2

var urlString : String?

//setup video player
func setupPlayerView() {

    print(urlString)

    //URL needed here
    if let videoURL = NSURL(string: urlString!){ //here the error occurs

我想补充一点，在第二类中尽快调用该函数非常重要。因此我没有使用 setupPlayerView(_urlString)...

因此，它目前看起来像这样(class 2，一个 UIView):

override init(frame: CGRect){

    super.init(frame: frame)

    //function below this override init
    setupPlayerView()

编辑:

首先感谢您的解答!尽管如此，仍然存在一个小问题(我认为立即调用该函数可以解决它......对于 swift 来说是一个新事物):即视频播放器(使用此函数设置)现在位于所有其他 subview 之上(一个只能看到覆盖整个屏幕的视频)尽管相反(视频使用整个屏幕但 subview 覆盖某些部分)。我将在下面提供更多关于添加其他 subview (所有这些都是闭包)和设置 View 的函数的代码。有没有办法让视频播放器保持在所有其他 subview 下方(即使它需要先从服务器加载)？你会建议我做什么？

下面的代码合并了第一个答案中的代码，但不一定要从那里开始

第 2 类

override init(frame: CGRect){

    super.init(frame: frame)

    setupPlayerView()

    //add subview with controls (e.g. spinner)
    controlsContainerView.frame = frame
    addSubview(controlsContainerView)

    //add to subview and center spinner in subview
    controlsContainerView.addSubview(activityIndicatorView)
    activityIndicatorView.centerXAnchor.constraint(equalTo: centerXAnchor).isActive = true
    activityIndicatorView.centerYAnchor.constraint(equalTo: centerYAnchor).isActive = true

    //add various subviews
    controlsContainerView.addSubview(whiteDummyView)
    controlsContainerView.addSubview(userProfilePicture)
    //... add further subviews

    //enable interaction
    controlsContainerView.isUserInteractionEnabled = true
    //... set to true for other subviews as well

    //function below this override init
    defInteractions()

    //backgorund color of player
    backgroundColor = .black

}

//create controls container view (a closure, like the (most of the) other subviews)
let controlsContainerView: UIView = {

    //set properties of controls container view
    let controlView = UIView()
    controlView.backgroundColor = UIColor(white: 0, alpha: 1)

    return controlView

}()

函数setupPlayerView()

//setup video player
func setupPlayerView() {

    //check URL if can be converted to NSURL
    if let urlString = self.urlString, let videoURL = NSURL(string: urlString){

        print(urlString)

        //player's video
        if self.player == nil {
            player = AVPlayer(url: videoURL as URL)
        }

        //add sub-layer
        let playerLayer = AVPlayerLayer(player: player)
        self.controlsContainerView.layer.addSublayer(playerLayer)
        playerLayer.frame = self.frame

        //when are frames actually rendered (when is video loaded)
        player?.addObserver(self, forKeyPath: "currentItem.loadedTimeRanges", options: .new, context: nil)

        //loop through video
        NotificationCenter.default.addObserver(forName: .AVPlayerItemDidPlayToEndTime, object: self.player?.currentItem, queue: nil, using: { (_) in
            DispatchQueue.main.async {
                self.player?.seek(to: kCMTimeZero)
                self.player?.play()
            }
        })

    }

}

Answer 1

如果没有太多关于类之间关系的上下文，看起来一个可能好的解决方案是使用属性观察者模式。

class Class2 {
    var urlString: String? {
        didSet {
            setupPlayerView()
        }
    }

    override init(frame: CGRect){
        super.init(frame: frame)
        setupPlayerView()
    }

    func setupPlayerView() {
        if let urlString = self.urlString, let videoURL = NSURL(string: urlString) {
            // do stuff here
        }
    }
}