如何在外部类的事件发生后更新SwiftUI按钮？

import SwiftUI
import Combine

class ButtonViewModel: ObservableObject {
    @Published var buttonTitle: String = "按钮"
    
    func updateButtonTitle() {
        // 外部事件发生后更新按钮标题
        buttonTitle = "更新后的按钮"
    }
}

struct ContentView: View {
    @ObservedObject var viewModel = ButtonViewModel()
    
    var body: some View {
        VStack {
            Button(action: {
                // 外部事件触发按钮标题更新
                self.viewModel.updateButtonTitle()
            }) {
                Text(viewModel.buttonTitle)
                    .font(.title)
                    .foregroundColor(.white)
                    .padding()
                    .background(Color.blue)
                    .cornerRadius(10)
            }
        }
    }
}