如何正确格式化附加到TextField的swift @Published didSet中的字符串？

import SwiftUI

class ViewModel: ObservableObject {
    @Published var inputText: String = ""
    @Published var formattedText: String = ""
    
    init() {
        // 监听inputText属性的变化，并在变化后格式化字符串
        $inputText
            .sink { [weak self] newValue in
                self?.formatText(newValue)
            }
            .store(in: &cancellables)
    }
    
    private var cancellables = Set<AnyCancellable>()
    
    private func formatText(_ text: String) {
        // 在这里进行字符串格式化操作，例如添加前缀、后缀
        let formattedString = "Formatted: " + text
        
        // 更新显示格式化后的字符串的TextField的绑定值
        formattedText = formattedString
    }
}

struct ContentView: View {
    @ObservedObject var viewModel = ViewModel()
    
    var body: some View {
        VStack {
            TextField("Enter text", text: $viewModel.inputText)
                .textFieldStyle(RoundedBorderTextFieldStyle())
            
            Text(viewModel.formattedText)
                .padding()
        }
        .padding()
    }
}

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