ios - 防止切换开关打开并在 Swiftui 中显示警报

Question

我有一些连续的拨动开关，但如果其中两个已经打开，我想防止开关打开。并显示一个警报，允许最多打开其中的 2 个。这是我的代码:

struct PreventToggle: View {

    @State private var isCheckeds = [false, true, true, false, false, false]
    @State var showAlert = false

    var body: some View {

        let numberOfTrue = isCheckeds.filter{$0}.count
        showAlert = numberOfTrue > 2

        return ForEach(0 ..< isCheckeds.count) { id in

                Toggle("Switch \(id)", isOn: self.$isCheckeds[id])
                    .alert(isPresented: self.$showAlert) {
                        Alert(title: Text("Maximum Limit!"), message: Text("Maximum limit is: 3"), dismissButton: .default(Text("Got it")))
                }
        }
    }
}

Answer 1

它是这样工作的:

struct PreventToggle: View {
  @State private var isCheckeds = [false, true, true, false, false, false]
  @State var lastSelected = -1

  func alertBinding() -> Binding<Bool> {
    Binding<Bool>(
      get: {
        let numberOfTrue = self.isCheckeds.filter{$0}.count
        return numberOfTrue > 2 && self.lastSelected != -1
      },
      set: { _ in }
    )
  }

  func toggleBinding(for index: Int) -> Binding<Bool> {
    Binding<Bool>(
      get: {
        return self.isCheckeds[index]
      },
      set: { bool in
        self.isCheckeds[index] = bool
        self.lastSelected = index
      }
    )
  }

  var body: some View {
    VStack {
      ForEach(0 ..< isCheckeds.count) { id in
        Toggle("Switch \(id)", isOn: self.toggleBinding(for: id))
      }
    }
    .alert(isPresented: alertBinding()) {
      Alert(title: Text("Maximum Limit!"),
            message: Text("Maximum limit is: 3"),
            dismissButton: .default(Text("Got it"), action: {
              self.isCheckeds[self.lastSelected] = false
              self.lastSelected = -1
            })
      )
    }
  }
}