NavigationSplitView绑定结构体失效，绑定ID正常的问题求助

你遇到的问题核心在于List的selection绑定类型与ForEach元素的匹配逻辑：

• 绑定整个Annotation对象时，SwiftUI依赖Hashable协议实现追踪选中状态，但默认合成的Hashable会使用结构体所有属性计算哈希值，这会导致状态更新识别失效；
• 绑定Annotation.ID（UUID）时，ID是唯一且稳定的标识，SwiftUI能准确追踪选中状态的变化，因此功能正常。

方案1：修正Annotation的Hashable实现 #

让Hashable和Equatable仅依赖id属性（唯一标识），确保SwiftUI能正确识别选中对象：

struct ContentView: View {
    var notes = [
        Annotation(title: "Note 1", details: "Some details here", completed: false),
        Annotation(title: "Note 2", details: "Some details here too", completed: true),
        Annotation(title: "Note 3", details: "Some details here also", completed: false)
    ]
    
    @State private var selected: Annotation?
        
    var body: some View {
        NavigationSplitView(columnVisibility: .constant(.doubleColumn)) {
            List (selection: $selected) {
                ForEach(notes) { annotation in
                    Text(annotation.title)
                }
            }
        } detail: {
            VStack {
                Text(selected?.title ?? "-")
                Text(selected?.details ?? "-")
            }
        }
    }
}

struct Annotation: Hashable, Identifiable {
    var id: UUID = UUID()
    var title: String
    var details: String
    var completed: Bool
    
    // 自定义哈希计算，仅基于id
    func hash(into hasher: inout Hasher) {
        hasher.combine(id)
    }
    
    // 自定义相等判断，仅比较id
    static func == (lhs: Annotation, rhs: Annotation) -> Bool {
        lhs.id == rhs.id
    }
}

方案2：保持绑定ID的方式（推荐） #

ID是更轻量、稳定的标识，尤其适合数据来自网络/数据库的场景。只需根据ID匹配对应的对象即可：

struct ContentView: View {
    var notes = [
        Annotation(title: "Note 1", details: "Some details here", completed: false),
        Annotation(title: "Note 2", details: "Some details here too", completed: true),
        Annotation(title: "Note 3", details: "Some details here also", completed: false)
    ]
    
    @State private var selectedId: Annotation.ID?
    
    // 根据ID获取选中对象
    private var selectedAnnotation: Annotation? {
        notes.first { $0.id == selectedId }
    }
        
    var body: some View {
        NavigationSplitView(columnVisibility: .constant(.doubleColumn)) {
            List (selection: $selectedId) {
                ForEach(notes) { annotation in
                    Text(annotation.title)
                }
            }
        } detail: {
            VStack {
                Text(selectedAnnotation?.title ?? "-")
                Text(selectedAnnotation?.details ?? "-")
            }
        }
    }
}

struct Annotation: Hashable, Identifiable {
    var id: UUID = UUID()
    var title: String
    var details: String
    var completed: Bool
}

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