在SwiftUI视图中实现委托

Question

我正在尝试实现需要委托方法（如NSUserActivity）的功能。因此，我需要一个UIViewController符合NSUserActivityDelegate（或类似的其他代表），处理并保存所有必需信息的。我的问题是我在界面上使用的是SwiftUI，因此我没有使用UIViewControllers。因此，我该如何实现此功能，同时仍将SwiftUI用于UI。我尝试了什么：view1只是一个普通的SwiftUI View，可以（通过NavigationLink）呈现view2，这是要实现此功能的视图。因此，我尝试了以下方法，而不是链接view1和view2，而是将view1链接到UIViewControllerRepresentable，然后处理该功能的实现并添加UIHostingController(rootView: view2)为子视图控制器。

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麻烦。所以我想知道是否有更好的方法在SwiftUI视图中实现这样的功能。

Answer 1

您需要创建一个符合UIViewControllerRepresentable并具有Coordinator处理所有委托功能的视图。

例如，使用您的示例视图控制器和委托：

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：我重命名VCRepresentable为SomeDelegateObserver更能说明它的作用：它的唯一目的是等待委托函数执行，然后运行foo您提供的闭包（即在此示例中）。您可以使用此模式创建尽可能多的函数以“观察”您关心的任何委托函数，然后执行可以更新 UI、数据模型等的代码。在我的示例中，当SomeDelegatefires 时someDelegateFunction(data:)，视图将显示“已执行”并更新数据实例变量。