SwiftUI NavigationStack迁移后绑定失效问题求助

从SwiftUI NavigationView迁移至NavigationStack后出现绑定失效问题：视图栈发生变化后，绑定变为局部状态，无法正常更新父视图的状态。

已将问题复现到简化场景：CounterView中用@State修饰counter变量，以绑定形式传递给EditCounterView。按以下步骤操作后绑定失效：

• 主页面 → CounterView → EditCounterView
• 返回至CounterView
• 返回至主页面 → OtherCounter
• 返回至主页面
• 主页面 → CounterView → EditCounterView（此时点击增减按钮，父视图counter无变化）
• 返回至CounterView，状态未更新
• 再次进入EditCounterView，状态恢复正常

代码示例：

import SwiftUI

@main
struct PlaygroundAppApp: App {
    
    @StateObject var router: Router = .init()

    var body: some Scene {
        WindowGroup {
            NavigationStack(path: self.$router.path) {
                Counters()
            }
            .environmentObject(self.router)
        }
    }
}

struct Other: Hashable {}
struct New: Hashable {}

final class Router: ObservableObject {
    @Published var path = NavigationPath()
}


struct Counters: View {
    @EnvironmentObject var router: Router

    var body: some View {
        VStack {
            NavigationLink("New Counter", value: New())
            
            NavigationLink("Other Counters", value: Other())
                .padding()
        }
        .navigationTitle("Main")
        .navigationDestination(for: New.self) { examination in
            CounterView()
        }
        .navigationDestination(for: Other.self) { examination in
            OtherCounter()
        }
    }
}


struct OtherCounter: View {
    var body: some View {
        VStack {
            NavigationLink("Counter", value: New())
        }
        .navigationTitle("Other Counter")
    }
}


struct CounterView: View {
    @State  private var counter: Int = 0
    
    var body: some View {
        VStack {
            NavigationLink("Edit counter", value: counter)
                    .padding()
                
            Text("COUNT \(self.counter)")
        }
        .navigationDestination(for: Int.self, destination: { value in
            EditCounterView(count: self.$counter)
        })
        .navigationTitle("Counter")
    }
}


struct EditCounterView: View {
    @Binding var count: Int

    var body: some View {
        VStack {
            Text("Current count \(count)")
           
            Button("increase") {
                self.count += 1
            }
            .padding()
            Button("decrease") {
                self.count -= 1
            }
        }
        .navigationTitle("Edit Counter")

    }
}

问题根源 #

问题出在**Int类型导航值与navigationDestination的匹配逻辑**：

1. 使用NavigationLink("Edit counter", value: counter)时，传递的是当前counter的数值（如0）作为导航标识。
2. navigationDestination(for: Int.self)会根据该数值匹配视图，但从OtherCounter返回主页面再进入CounterView时，新CounterView的counter初始值仍是0，与之前的导航值重复。
3. NavigationStack会复用之前缓存的EditCounterView实例，而该实例绑定的是已销毁的旧CounterView的counter状态，导致新CounterView无法接收更新。

解决方案 #

方案1：用唯一标识的自定义类型替代Int作为导航值 #

创建专门的导航类型，确保每次导航标识唯一，避免复用旧视图：

// 新增专门的导航类型
struct EditCounter: Hashable {}

// 修改CounterView
struct CounterView: View {
    @State private var counter: Int = 0
    
    var body: some View {
        VStack {
            // 使用自定义类型作为导航值
            NavigationLink("Edit counter", value: EditCounter())
                    .padding()
                
            Text("COUNT \(self.counter)")
        }
        // 匹配自定义类型
        .navigationDestination(for: EditCounter.self) { _ in
            EditCounterView(count: self.$counter)
        }
        .navigationTitle("Counter")
    }
}

方案2：直接在NavigationLink中指定目标视图 #

绕过NavigationStack的全局匹配缓存，直接在NavigationLink里定义目标视图：

struct CounterView: View {
    @State private var counter: Int = 0
    
    var body: some View {
        VStack {
            // 直接指定destination，不依赖全局匹配
            NavigationLink("Edit counter") {
                EditCounterView(count: self.$counter)
            }
                    .padding()
                
            Text("COUNT \(self.counter)")
        }
        .navigationTitle("Counter")
    }
}

方案3：给Int导航值添加唯一标识 #

若必须使用Int，可结合视图唯一ID生成导航值，确保每次导航标识不重复：

struct CounterView: View {
    @State private var counter: Int = 0
    // 生成视图唯一ID
    private let viewId = UUID()
    
    var body: some View {
        VStack {
            // 使用组合值作为导航标识
            NavigationLink("Edit counter", value: "\(viewId)-\(counter)")
                    .padding()
                
            Text("COUNT \(self.counter)")
        }
        // 匹配字符串类型
        .navigationDestination(for: String.self) { _ in
            EditCounterView(count: self.$counter)
        }
        .navigationTitle("Counter")
    }
}

内容的提问来源于stack exchange，提问作者Dunderklaepp