swift - 在选择器上显示警报选择 SwiftUI

Question

我想在用户在表单选择器中选择某些内容时显示一个警报框，然后用户必须在值更改之前确认他们的选择。现在我的代码如下所示(仅来自一些教程):

            NavigationView {
            Form {
                Section {
                    Picker("Strength", selection: $selectedStrength) {
                        ForEach(strengths, id: \.self) {
                            Text($0)
                        
                            
                        }
                    }
                }
            }
        }

我尝试过使用 onChange() 但理想情况下应该在值更改之前进行检查。

Answer 1

如果您想在选择更改之前要求用户确认，您需要使用第二个变量实现自定义绑定(bind)。这样您就可以在必要时取消选择。

struct Test: View{
    @State private var selectedStrength: String = ""
    @State private var askForStrength: String = ""
    @State private var ask: Bool = false
    let strengths = ["1","2","3"]
    var body: some View{
        NavigationView {
            Form {
                Section {
                    Picker("Strength", selection: Binding(get: {selectedStrength}, set: {
                        //assign the selection to the temp var
                        askForStrength = $0
                        // show the Alert
                        ask = true
                    })) {
                        ForEach(strengths, id: \.self) {
                            Text($0)
                        }
                    }
                }
            }
        }.alert(isPresented: $ask) {
            // Here ask the user if selection is correct and apply the temp var to the selection
            Alert(title: Text("select?"), message: Text("Do you want to select \(askForStrength)"), primaryButton: .default(Text("select"), action: {selectedStrength = askForStrength}), secondaryButton: .cancel())
        }
    }
}