只有根级导航目的地对具有同构路径的导航堆栈有效

Question

我正在尝试将 NavigationStack 集成到我的 SwiftUI 应用程序中，我有四个视图 CealUIApp、OnBoardingView、UserTypeView 和 RegisterView。当用户按下OnBoardingView中的按钮时，我想从OnBoardingView导航到UserTypeView，当用户按下UserTypeView 中的按钮时，我想从UserTypeView导航到RegisterView

下面是我的 CealUIApp 代码

@main
struct CealUIApp: App {
    
    @State private var path = [String]()
    
    var body: some Scene {
        WindowGroup {
            NavigationStack(path: $path){
                OnBoardingView(path: $path)
            }
        }
    }
}

在OnBoardingView

Button {
                    path.append("UserTypeView")
                } label: {
                    Text("Hello")
                }.navigationDestination(for: String.self) { string in
                    UserTypeView(path: $path)
                }

在UserTypeView

Button {
                path.append("RegisterView")
            } label: {
                Text("Hello")
            }.navigationDestination(for: String.self) { string in
                RegisterView()
            }

当按下UserTypeView中的按钮时，我不断导航到UserTypeView而不是RegisterView，Xcode中的消息显示Only root-level navigation destinations are effective for a navigation stack with a homogeneous path.

Answer 1

您可以通过将路径类型更改为 NavigationPath 来删除 Only root-level navigation destinations are effective for a navigation stack with a homogeneous path。

@State private var path: NavigationPath = .init()

但是随后您收到一条消息/错误，我认为它可以更好地解释问题A navigationDestination for “Swift.String” was declared earlier on the stack. Only the destination declared closest to the root view of the stack will be used.

Apple 决定扫描所有可用的视图效率非常低，因此他们将优先使用 navigationDestination。

试想一下，如果您的OnBoardingView也有"RegisterView"的选项

 .navigationDestination(for: String.self) { string in
        switch string{
        case "UserTypeView":
            UserTypeView(path: $path)
        case "RegisterView":
            Text("fakie register view")
        default:
            Text("No view has been set for (string)")
        }
        
    }

SwiftUI 将如何选择合适的？

那么如何“修”呢？您可以尝试这种替代方法。

import SwiftUI

@available(iOS 16.0, *)
struct CealUIApp: View {
    @State private var path: NavigationPath = .init()
    var body: some View {
        NavigationStack(path: $path){
            OnBoardingView(path: $path)
                .navigationDestination(for: ViewOptions.self) { option in
                    option.view($path)
                }
        }
    }
    //Create an `enum` so you can define your options
    enum ViewOptions{
        case userTypeView
        case register
        //Assign each case with a `View`
        @ViewBuilder func view(_ path: Binding<NavigationPath>) -> some View{
            switch self{
            case .userTypeView:
                UserTypeView(path: path)
            case .register:
                RegisterView()
            }
        }
    }
}
@available(iOS 16.0, *)
struct OnBoardingView: View {
    @Binding var path: NavigationPath
    var body: some View {
        Button {
            //Append to the path the enum value
            path.append(CealUIApp.ViewOptions.userTypeView)
        } label: {
            Text("Hello")
        }
        
    }
}
@available(iOS 16.0, *)
struct UserTypeView: View {
    @Binding var path: NavigationPath
    var body: some View {
        Button {
            //Append to the path the enum value
            path.append(CealUIApp.ViewOptions.register)
        } label: {
            Text("Hello")
        }
        
    }
}
@available(iOS 16.0, *)
struct RegisterView: View {
    var body: some View {
        Text("Register")
        
    }
}
@available(iOS 16.0, *)
struct CealUIApp_Previews: PreviewProvider {
    static var previews: some View {
        CealUIApp()
    }
}

Answer 2

按照@lorem ipsum 示例，我认为您可以使用@ObservableObject 更改此状态变量 @State private var path: NavigationPath = .init()，这样您就不需要在所有视图上传递@Bindings。您只需将它从 CealUIApp 视图作为 WnvironmentObject 传递下来

class NavigationStack: ObservableObject {
    @Published var paths: NavigationPath = .init()
}


@main
struct CealUIApp: App {
    
    let navstack = NavigationStack()
    
    var body: some Scene {
        WindowGroup {
                AppEntry()
                    .environmentObject(navstack)
        }
    }
}

extension CealUIApp {
    enum ScreenDestinations {
        case userTypeView
        case registerView
        
        
        //Assign each case with a `View`
        @ViewBuilder func view(_ path: Binding<NavigationPath>) -> some View {
            switch self{
                case .permissions:
                    UserTypeView()
                case .seedPhrase:
                    RegisterView()
            }
        }
    }

}


// An extra view after the AppView

struct AppEntry: View {
    
    @EnvironmentObject var navStack: NavigationStack
    
    var body: some View {
        NavigationStack(path: $navStack.paths) {
            OnBoardingView()
                .navigationDestination(for: CealUIApp.ScreenDestinations.self) {
                    $0.view($navStack.paths)
                }
        }
    }
}

然后其余的与@lorem ipsum 所说的相同。