SwiftUI 选项卡选择不适用于任何可哈希内容

Question

SwiftUI\xe2\x80\x99s 选项卡选择应该适用于任何可哈希的内容，但这似乎不起作用。

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在提供的示例中，您可以看到在 \xe2\x80\x9cWorking\xe2\x80\x9d Tab 中，如果您使用整数作为选项卡选择，则所有内容都可以正常工作。当您切换到 \xe2\x80\x9cBroken\xe2\x80\x9d 选项卡时，选择的是 ColorItem，并且选择不会更新视图。

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我相信这是一个 SwiftUI 错误并已提交反馈（FB8879981）。

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使用 Xcode 12.2 和 iOS 14.2(RC) 进行测试。

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struct ColorItem: Identifiable, Hashable{\n    let color: Color\n    let title: String\n    \n    var id: String{\n        title\n    }\n}\n

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struct ContentView: View {\n    let items = [\n        ColorItem(color: .red, title: "Red"),\n        ColorItem(color: .blue, title: "Blue"),\n        ColorItem(color: .purple, title: "Purple")\n    ]\n    \n    var body: some View {\n        TabView{\n            TabViewWorking(items: items)\n                .tabItem {\n                    Label("Working", systemImage: "hand.thumbsup")\n                }\n            \n            TabViewBroken(items: items)\n                .tabItem {\n                    Label("Broken", systemImage: "hand.thumbsdown")\n                }\n        }\n    }\n}\n

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struct TabViewWorking: View {\n    @State private var tabSelection = 0\n    let items: [ColorItem]\n    \n    var body: some View {\n        ZStack{\n            TabView(selection: $tabSelection){\n                ForEach(0..<items.count){ i in\n                    items[i].color.edgesIgnoringSafeArea(.all)\n                        .tag(i)\n                }\n            }\n            .tabViewStyle(PageTabViewStyle())\n            \n            VStack{\n                Text(tabSelection.description)\n                Text(items[tabSelection].title)\n            }\n            .font(.largeTitle)\n        }\n    }\n}\n

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struct TabViewBroken: View {\n    @State private var tabSelection = ColorItem(color: .red, title: "Red")\n    let items: [ColorItem]\n\n    var body: some View {\n        ZStack{\n            TabView(selection: $tabSelection){\n                ForEach(0..<items.count){ i in\n                    items[i].color.edgesIgnoringSafeArea(.all)\n                        .tag(i)\n                }\n            }\n            .tabViewStyle(PageTabViewStyle())\n            \n            VStack{\n                Text(items.firstIndex(of: tabSelection)?.description ?? "N/A")\n                Text(tabSelection.title)\n            }\n            .font(.largeTitle)\n        }\n    }\n}\n

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Answer 1

不，这不是 SwiftUI 错误。选择的类型和标签的类型必须相同，因此在第一个场景中它们都是整数，但在第二个场景中它们不同 - 选择是ColorItem，但标签仍然是整数 - 因此选择不起作用。

这是固定变体：

struct TabViewBroken: View {
    @State private var tabSelection = ColorItem(color: .red, title: "Red")
    let items: [ColorItem]

    var body: some View {
        ZStack{
            TabView(selection: $tabSelection){
                ForEach(0..<items.count){ i in
                    items[i].color.edgesIgnoringSafeArea(.all)
                        .tag(items[i])                          // << here !!     
                }
            }
            .tabViewStyle(PageTabViewStyle())
            
            VStack{
                Text(items.firstIndex(of: tabSelection)?.description ?? "N/A")
                Text(tabSelection.title)
            }
            .font(.largeTitle)
        }
    }
}