通过取消关闭首选项视图时恢复@AppStorage

Question

考虑以表格形式呈现的以下

PreferencesView

：

struct PreferencesView: View {
    @Environment(\.dismiss) private var dismiss

    @AppStorage("setting1") var setting1: Bool = true
    @AppStorage("setting2") var setting2: Bool = false
    @AppStorage("setting3") var setting3: Bool = false
    // many more

    var body: some View {
        NavigationView {
            Form {
                Toggle("Setting 1", isOn: $setting1)
                Toggle("Setting 2", isOn: $setting2)
                Toggle("Setting 3", isOn: $setting3)
            }
            .navigationTitle("Preferences")
            .toolbar {
                ToolbarItem(placement: .navigationBarLeading) {
                    Button("Cancel") {
                        reset()

                        dismiss()
                    }
                }
                ToolbarItem(placement: .navigationBarTrailing) {
                    Button("Save") {
                        dismiss()
                    }
                }
            }
        }
    }

    private func reset() {
        // what do I put here?
    }
}

如果用户点击取消，我希望将设置值设置回打开工作表时的值。我可以添加单独的

initialSetting1

等属性，然后在

reset

函数中添加

setting1 = initialSetting1

。但设置很多就变得乏味了。

还有别的办法吗？

Answer 1

• 使用

  onAppear

加载当前设置
• 使用本地

  @State

  绑定到切换开关
• 当用户按下“保存”按钮时，将当前值从

  @State

  保存到设置。

像这样：

struct PreferencesView: View {
    @Environment(\.dismiss) private var dismiss

    @AppStorage("setting1") var setting1: Bool = true
    @AppStorage("setting2") var setting2: Bool = false
    @AppStorage("setting3") var setting3: Bool = false
    
    // Initial value doesn't matter, will be overwritten
    @State var currentSetting1: Bool = false
    @State var currentSetting2: Bool = false
    @State var currentSetting3: Bool = false
    // many more

    var body: some View {
        NavigationView {
            Form {
                // Change internal state, not settings
                Toggle("Setting 1", isOn: $currentSetting1)
                Toggle("Setting 2", isOn: $currentSetting2)
                Toggle("Setting 3", isOn: $currentSetting3)
            }
            .navigationTitle("Preferences")
            .toolbar {
                ToolbarItem(placement: .navigationBarLeading) {
                    Button("Cancel") {
                        // No need to do anything here
                        dismiss()
                    }
                }
                ToolbarItem(placement: .navigationBarTrailing) {
                    Button("Save") {
                        // Save current internal state to settings
                        setting1 = currentSetting1
                        setting2 = currentSetting2
                        setting3 = currentSetting3
                        dismiss()
                    }
                }
            }
            .onAppear() {
                // Load settings
                currentSetting1 = setting1
                currentSetting2 = setting2
                currentSetting3 = setting3
            }
        }
    }
}