我希望iOS11版本能够解决静音推送的问题，这个问题出现在最新的betas和GM版本的iOS中。

目前我很难理解，为什么我没有收到任何静默推送消息，这些消息实际上应该唤醒我的应用程序，在后台执行一些需要的任务。

在iOS 10中，我只使用后台提取功能，并在AppDelegate中实现了“唤醒代码”，如下所示。

在iOS 11中，注册代码仍然运行良好，我的后端也将推送通知发送到Apples DEV服务器（沙箱）和PROD服务器（生产版本）。不幸的是，静默推送通知从不调用函数Void)/code>。

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@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

  // .. some variables here ...

   func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

       // register silent push notification in backend
       application.registerForRemoteNotifications()

       // ... some code here ... 


       // Set Background Fetch Intervall for background services / terminated app
       UIApplication.shared.setMinimumBackgroundFetchInterval(UIApplicationBackgroundFetchIntervalMinimum)

       // ... some code here ... 

       return true
   }

   func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
       let tokenParts = deviceToken.map { data -> String in
           return String(format: "%02.2hhx", data)
       }
       let token = tokenParts.joined()
       logger.log.debug("Device Token: \(token)")

       let realm = RealmController()
       let user = realm.getLoggedInUserObject()

       // Send push token to server
       if let user = user {
           let email = user.email!

           let serverController = ServerController.serverController
           serverController.sendPushToken(token: token, email: email) { status in
               if status == 201 {
                // ... some code here ...
               } else {
               // ... some code here ...
               }
           }
       }
   }
   func application(_ application: UIApplication, didFailToRegisterForRemoteNotificationsWithError error: Error) {
       logger.log.debug(error)
   }
   func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
       logger.log.debug(userInfo)

       let aps = userInfo["aps"] as! [String: AnyObject]
       if aps["content-available"] as? Int == 1 {
          // .... some silent push tasks here ....
       }
   }
}