如何使用 SwiftUI 连续呈现两个警报视图

Question

I want to immediately present the second alert view after click the dismiss button of the first alert view.

Button(action: {
     self.alertIsVisible = true
}) {
     Text("Hit Me!")
}
.alert(isPresented: $alertIsVisible) { () -> Alert in
    return Alert(title: Text("\(title)"), message: Text("\n"), dismissButton:.default(Text("Next Round"), action: {
        if self.score == 100 {
            self.bonusAlertIsVisible = true
    }
    .alert(isPresented: $bonusAlertIsVisible) {
        Alert(title: Text("Bonus"), message: Text("You've earned 100 points bonus!!"), dismissButton: .default(Text("Close")))}
})
)

However, it gives me an error of 'Alert.Button' is not convertible to 'Alert.Button?' If I put this segment out of the scope of dismissButton, it will override the previous.alert. So how can i do it, I just want to pop up the second alert after clicking the dismiss button of the first alert. Thanks.

Answer 1

It appears (tested with Xcode 11.2):

1. While not documented, but it is not allowed to add more than one.alert modifier in one view builder sequence - works only latest
2. It is not allowed to add.alert modifier to EmptyView, it does not work at all

I've found alternate solution to proposed by @Rohit. In some situations, many alerts, this might result in simpler code.

struct TestTwoAlerts: View {
    @State var alertIsVisible = false
    @State var bonusAlertIsVisible = false

    var score = 100
    var title = "First alert"

    var body: some View {
        VStack {
            Button(action: {
                 self.alertIsVisible = true
            }) {
                 Text("Hit Me!")
            }
            .alert(isPresented: $alertIsVisible) {
                Alert(title: Text("\(title)"), message: Text("\n"), dismissButton:.default(Text("Next Round"), action: {
                    if self.score == 100 {
                        DispatchQueue.main.async { // !! This part important !!
                            self.bonusAlertIsVisible = true
                        }
                    }
                }))
            }
            Text("")
            .alert(isPresented: $bonusAlertIsVisible) {
                    Alert(title: Text("Bonus"), message: Text("You've earned 100 points bonus!!"), dismissButton: .default(Text("Close")))
            }
        }
    }
}

backup

Answer 2

Please try below code.

Consecutively present two alert views using SwiftUI

struct ContentView: View {

    @State var showAlert: Bool = false
    @State var alertIsVisible: Bool = false
    @State var bonusAlertIsVisible: Bool = false

    var body: some View {

        NavigationView {

            Button(action: {
                self.displayAlert()
            }) {
                Text("Hit Me!")
            }
            .alert(isPresented: $showAlert) { () -> Alert in
                if alertIsVisible {
                    return Alert(title: Text("First alert"), message: Text("\n"), dismissButton:.default(Text("Next Round"), action: {
                        DispatchQueue.main.async {
                            self.displayAlert()
                        }
                     })
                   )
                }
                else {
                    return Alert(title: Text("Bonus"), message: Text("You've earned 100 points bonus!!"), dismissButton:.default(Text("Close"), action: {
                                self.showAlert = false
                                self.bonusAlertIsVisible = false
                                self.alertIsVisible = false
                        })
                    )
                }
            }
            .navigationBarTitle(Text("Alert"))
        }
    }

    func displayAlert() {

       self.showAlert = true
       if self.alertIsVisible == false {
            self.alertIsVisible = true
            self.bonusAlertIsVisible = false
       }
       else {
            self.alertIsVisible = false
            self.bonusAlertIsVisible = true
       }
    }
}