SwiftUI:如何从ViewModel中的更改切换警报呈现器

class ViewModel: ObservableObject {
    @Published var showAlert = false
    @Published var alertMessage = ""
    
    func toggleAlert() {
        showAlert.toggle()
    }
    
    func updateAlertMessage(_ message: String) {
        alertMessage = message
    }
}

struct ContentView: View {
    @StateObject private var viewModel = ViewModel()
    @State private var userInput = ""
    
    var body: some View {
        VStack {
            TextField("Enter message", text: $userInput)
                .padding()
            
            Button("Toggle Alert") {
                viewModel.toggleAlert()
            }
        }
        .alert(isPresented: $viewModel.showAlert) {
            Alert(title: Text("Alert"), message: Text(viewModel.alertMessage), dismissButton: .default(Text("OK")))
        }
        .onChange(of: userInput) { newValue in
            viewModel.updateAlertMessage(newValue)
        }
    }
}