我正在尝试实现需要委托(delegate)方法的功能(如 NSUserActivity)。因此，我需要一个符合 NSUserActivityDelegate(或类似的其他委托(delegate))的 UIViewController，处理并保存所有必需的信息。我的问题是我的界面使用 SwiftUI，因此我没有使用 UIViewControllers。那么我怎样才能实现这个功能并仍然使用 SwiftUI 作为 UI。我尝试了什么:view1 只是一个普通的 SwiftUI View，它可以呈现(通过 NavigationLink)view2，它是想要实现此功能的 View 。所以我尝试不链接 view1 和 view2，而是将 view1 链接到 UIViewControllerRepresentable，然后处理此功能的实现并添加 UIHostingController(rootView: view2) 作为 subview Controller .

struct view1: View {    
    var body: some View {
        NavigationLink(destination: VCRepresentable()) {
            Text("Some Label")
        }
    }
}

struct view2: View {    
    var body: some View {
        Text("Hello World!")
    }
}

struct VCRepresentable: UIViewControllerRepresentable {
    func makeUIViewController(context: Context) -> UIViewController {
        return implementationVC()
    }

    func updateUIViewController(_ uiViewController: UIViewController, context: Context) { }
}

class implementationVC: UIViewController, SomeDelegate for functionality {
    // does implementation stuff in delegate methods
    ...

    override func viewDidLoad() {
        super.viewDidLoad()

        attachChild(UIHostingController(rootView: view2()))
    }

    private func attachChild(_ viewController: UIViewController) {
        addChild(viewController)

        if let subview = viewController.view {
            subview.translatesAutoresizingMaskIntoConstraints = false
            view.addSubview(subview)

            subview.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
            subview.heightAnchor.constraint(equalTo: view.heightAnchor).isActive = true
            subview.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
            subview.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
        }

        viewController.didMove(toParent: self)
    }
}

我在 VC 和 view2 之间传输数据时遇到问题。所以我想知道是否有更好的方法在 SwiftUI View 中实现这样的功能。

最佳答案

您需要创建一个符合 UIViewControllerRepresentable 并具有处理所有委托(delegate)功能的 Coordinator 的 View 。

例如，对于您的示例 View Controller 和委托(delegate):

struct SomeDelegateObserver: UIViewControllerRepresentable {
    let vc = SomeViewController()
    var foo: (Data) -> Void
    func makeUIViewController(context: Context) -> SomeViewController {
        return vc
    }

    func updateUIViewController(_ uiViewController: SomeViewController, context: Context) { }
    func makeCoordinator() -> Coordinator {
        Coordinator(vc: vc, foo: foo)
    }

    class Coordinator: NSObject, SomeDelegate {
        var foo: (Data) -> Void
        init(vc: SomeViewController, foo: @escaping (Data) -> Void) {
            self.foo = foo
            super.init()
            vc.delegate = self
        }
        func someDelegateFunction(data: Data) {
            foo(data)
        }
    }
}

用法:

struct ContentView: View {
    var dataModel: DataModel

    var body: some View {
        NavigationLink(destination: CustomView(numberFromPreviousView: 10)) {
            Text("Go to VCRepresentable")
        }
    }
}

struct CustomView: View {
    @State var instanceData1: String = ""
    @State var instanceData2: Data?
    var numberFromPreviousView: Int // example of data passed from the previous view to this view, the one that can react to the delegate's functions
    var body: some View {
        ZStack {
            SomeDelegateObserver { data in
                print("Some delegate function was executed.")
                self.instanceData1 = "Executed!"
                self.instanceData2 = data
            }
            VStack {
                Text("This is the UI")
                Text("That, in UIKit, you would have in the UIViewController")
                Text("That conforms to whatever delegate")
                Text("SomeDelegateObserver is observing.")
                Spacer()
                Text(instanceData1)
            }
        }
    }
}

注意:我将 VCRepresentable 重命名为 SomeDelegateObserver 以更好地说明它的作用:它的唯一目的是等待委托(delegate)函数执行然后运行您提供的闭包(即本例中的 foo)。您可以使用此模式创建尽可能多的函数来“观察”您关心的任何委托(delegate)函数，然后执行可以更新 UI、数据模型等的代码。在我的示例中，当 SomeDelegate 触发 someDelegateFunction(data:)， View 将显示“Excuted”并更新数据实例变量。

关于swift - 在 SwiftUI View 中实现委托(delegate)，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/57281389/