试图访问由另一个场景委托函数在场景委托中创建的环境对象

Question

我在我的场景委托中创建了一个环境对象，并且还想在我的场景委托中的另一个函数中使用它。代码如下：

SceneDelegate.swift

    class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    
        var window: UIWindow?
        //@EnvironmentObject var data: DataFetcher
        var data = DataFetcher()
    
        func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
 
            if let windowScene = scene as? UIWindowScene {
                
                let window = UIWindow(windowScene: windowScene)
                let data = (UIApplication.shared.delegate as! AppDelegate).self.data
                window.rootViewController = UIHostingController(rootView: ContentView().environmentObject(data))
                self.window = window
                window.makeKeyAndVisible()
            }
        }
        
        func handleIncomingDynamicLink(_ dynamicLink: DynamicLink){
            guard let url = dynamicLink.url else {
                print("That's weird. My dynamic link object has no url")
                return
            }
            print("Your incoming link parameter is \(url.absoluteString)")
            guard let components = URLComponents(url: url, resolvingAgainstBaseURL: false),
                let queryItems = components.queryItems else {return}
            self.data.linkRecieved = true
            print(data.linkRecieved)
        }
func scene(_ scene: UIScene, continue userActivity: NSUserActivity) {
        if let incomingURL = userActivity.webpageURL {
            print("Incoming URL is \(incomingURL)")
            _ = DynamicLinks.dynamicLinks().handleUniversalLink(incomingURL) { (dynamicLink, error) in
                guard error == nil else{
                    print("Found an error! \(error!.localizedDescription)")
                    return
                }
                if let dynamicLink = dynamicLink {
                    self.handleIncomingDynamicLink(dynamicLink)
                }
            }
        }
    }
        

问题是在执行handleIncomingDynamicLink 函数时，环境对象的linkRecieved 变量在contentview 内没有改变（我已经验证该变量在函数运行后确实变为true）。非常感谢解决此问题的任何见解！！！

Answer 1

您已将DataFetcher 实例分配给data 属性，大概是为了设置其类型并消除您的属性未初始化的错误。

然后在willConnectTo 中，您会从您的AppDelegate. Your dataproperty and the localdatavariable inwillConnectTo(That you subsequently add to the environment) now reference different instances ofDataFetcher` 中获得DataFetcher 实例，但您没有意识到。

出于这个原因，我不太喜欢将“丢弃”实例分配给属性。

更好的方法是使用隐式展开的可选项。这样一来，如果您不为该属性分配值，您将遇到崩溃并迅速找出问题所在。

然后在willConectTo 中，您可以将AppDelegate 中的实例分配给属性并将其放入环境中。

class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    
        var window: UIWindow?
        //@EnvironmentObject var data: DataFetcher
        var data: DataFetcher!
    
        func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
 
            if let windowScene = scene as? UIWindowScene {
                
                let window = UIWindow(windowScene: windowScene)
                self.data = (UIApplication.shared.delegate as! AppDelegate).self.data
                window.rootViewController = UIHostingController(rootView: ContentView().environmentObject(data))
                self.window = window
                window.makeKeyAndVisible()
            }
        }

Answer 2

你需要注入 var data 这是属性，所以删除以下行

let window = UIWindow(windowScene: windowScene)
//let data = (UIApplication.shared.delegate as! AppDelegate).self.data // << this one
window.rootViewController = UIHostingController(rootView: 
   ContentView().environmentObject(self.data))   // << inject own property