如何通过代码或自定义类在swiftui中显示警报

struct ContentView: View {
    @State private var showAlert = false
    
    var body: some View {
        Button("显示警报") {
            showAlert = true
        }
        .alert(isPresented: $showAlert) {
            Alert(title: Text("警报"), message: Text("这是一个警报示例"), dismissButton: .default(Text("确定")))
        }
    }
}

struct ContentView: View {
    @State private var showAlert = false
    
    var body: some View {
        Button("显示警报") {
            showAlert = true
        }
        .sheet(isPresented: $showAlert) {
            CustomAlert(showAlert: $showAlert)
        }
    }
}

struct CustomAlert: View {
    @Binding var showAlert: Bool
    
    var body: some View {
        VStack {
            Text("这是一个自定义警报")
                .font(.title)
                .padding()
            
            Button("确定") {
                showAlert = false
            }
            .padding()
        }
    }
}