使SwiftUI文档以EnvironmentObject格式提供

import SwiftUI
import Combine

class UserPreferences: ObservableObject {
    @Published var theme: String = "light"
    @Published var fontSize: Int = 16
}

import SwiftUI

class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    var window: UIWindow?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        let contentView = ContentView()
            .environmentObject(UserPreferences())

        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: contentView)
            self.window = window
            window.makeKeyAndVisible()
        }
    }
}

import SwiftUI

struct ContentView: View {
    @EnvironmentObject var userPreferences: UserPreferences

    var body: some View {
        VStack {
            Text("Current Theme: \(userPreferences.theme)")
            Button(action: {
                self.userPreferences.theme = self.userPreferences.theme == "light" ? "dark" : "light"
            }) {
                Text("Toggle Theme")
            }
        }
    }
}

struct ContentView: View {
    @EnvironmentObject var userPreferences: UserPreferences // 确保这里声明了 EnvironmentObject
    // ...
}

class UserPreferences: ObservableObject {
    @Published var theme: String = "light" // 使用 @Published
    // ...
}