如何在没有按钮的SwiftUI中显示警报

import SwiftUI

struct ContentView: View {
    @State private var showAlert = false
    
    var body: some View {
        VStack {
            Text("Hello, SwiftUI!")
                .font(.title)
                .padding()
            
            Button("Show Alert") {
                showAlert = true
            }
        }
        .alert(isPresented: $showAlert) {
            Alert(title: Text("Alert"), message: Text("This is an alert"), dismissButton: .default(Text("OK")))
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}