Swift 闭包回调报错： C function pointer cannot be formed from a closure that captures context

最近在写 flutter 跟 ios swift 原生通信的 demo，遇到一个问题，报这个错：

C function pointer cannot be formed from a closure that captures context

代码如下：

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

    
    CFNotificationCenterAddObserver(center, Unmanaged.passUnretained(self).toOpaque(), { (center, observer, name, object, userInfo) in
                  
        NSLog("Notify received")
        CustomChannel.sendMessageToFlutter(controller: controller)

public struct CustomChannel {
    
    static func sendMessageToFlutter(controller: FlutterViewController){
        let channel = FlutterMethodChannel(
            name: "paymentview",
            binaryMessenger: controller.binaryMessenger
        )

        DispatchQueue.main.async {
            channel.invokeMethod("authorized", arguments: nil)
                   }
    }
}

swift 现在是边学边写，这个闭包看起来有点看不懂。