如何使用Firebase数据创建和填充SwiftUI列表？

import SwiftUI
import Firebase

struct Todo: Identifiable {
    let id: String
    let title: String
    let completed: Bool
}

class TodoViewModel: ObservableObject {
    @Published var todos: [Todo] = []
    
    init() {
        // 配置Firebase数据库
        FirebaseApp.configure()
        let db = Firestore.firestore()
        
        // 监听todos集合中的数据变化
        db.collection("todos").addSnapshotListener { (querySnapshot, error) in
            guard let documents = querySnapshot?.documents else {
                print("Error fetching documents: \(error!)")
                return
            }
            
            // 清空现有的todos列表
            self.todos.removeAll()
            
            // 遍历查询结果，创建Todo对象并添加到todos列表中
            for document in documents {
                let data = document.data()
                let id = document.documentID
                let title = data["title"] as? String ?? ""
                let completed = data["completed"] as? Bool ?? false
                
                let todo = Todo(id: id, title: title, completed: completed)
                self.todos.append(todo)
            }
        }
    }
}

struct TodoListView: View {
    @ObservedObject var viewModel = TodoViewModel()
    
    var body: some View {
        List(viewModel.todos) { todo in
            VStack(alignment: .leading) {
                Text(todo.title)
                    .font(.headline)
                Text(todo.completed ? "Completed" : "Not Completed")
                    .font(.subheadline)
            }
        }
    }
}

struct ContentView: View {
    var body: some View {
        NavigationView {
            TodoListView()
                .navigationBarTitle("Todo List")
        }
    }
}

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