AppDelegate.swift

import FlutterPluginRegistrant

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
  
    lazy var flutter_engine = FlutterEngine(name: "flutter_engine")
  
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        flutter_engine.run()
        GeneratedPluginRegistrant.register(with: self.flutter_engine)
        return true
    }
}