如何使用Pigeon包从Flutter调用原生iOS函数？

dependencies:
  flutter:
    sdk: flutter
  pigeon: ^0.1.0

import 'package:pigeon/pigeon.dart';

class FlutterApi {
  Future<void> callNativeFunction(String argument) async {}
}

@HostApi()
abstract class NativeApi {
  void nativeFunction(String argument);
}

import Flutter
import UIKit

public class NativeApiImpl: NSObject, FlutterApi {
  public func callNativeFunction(argument: String?, error: AutoreleasingUnsafeMutablePointer<FlutterError?>) {
    // 在这里实现原生iOS函数的逻辑
  }
}

import UIKit
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    let controller : FlutterViewController = window?.rootViewController as! FlutterViewController
    let api = NativeApiImpl()
    FlutterApiSetup(controller.binaryMessenger, api: api)
    GeneratedPluginRegistrant.register(with: self)
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}

import 'package:flutter/material.dart';
import 'package:pigeon/pigeon.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  final FlutterApi api = FlutterApi();

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter App'),
        ),
        body: Center(
          child: RaisedButton(
            child: Text('Call Native Function'),
            onPressed: () {
              api.callNativeFunction('Hello from Flutter');
            },
          ),
        ),
      ),
    );
  }
}