How to access the Swift struct conforming to the App protocol from the AppDelegate

Question

Sorry if this is an answered question but 'Swift' 'App' and 'Protocol' are all too generic terms to warrant a good result.

I have socket emulator app that I use for testing that has a App struct with the server as a property:

@main
struct RelayEmulatorApp: App {

   var socketServer : SocketServer


   @NSApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
}

And then in my appDelegate I override applicationWillTerminate where I would like to gracefully close the socket server. I'm finding since the socketServer's deinit has the calls to NIO's syncShutdownGracefully which is not called on app termination, I have to call it explicitly in AppDelegate (the OS apparently is slow to close the socket for a terminated process when the process doesn't do so--I think).

class AppDelegate: NSObject, NSApplicationDelegate {

  func applicationWillTerminate(_ notification: Notification) {

  }

}

But how in the AppDelegate can I reference the instance of the App struct (which I imagine is being instantiated by the @main annotation) and thus its properties to gracefully shutdown the socket?

Does this answer your question https://stackoverflow.com/a/63597866/12299030? — Asperi, Jun 04 '21 at 11:31
Well, it could but I think I prefer Tarun Tyagi's solution of injecting the bits needed over depending on a singleton GOD AppState object as suggested in that solution. — Scott, Jun 05 '21 at 16:45

score 0 · Accepted Answer · answered Jun 04 '21 at 06:35

Inside the RelayEmulatorApp, after the socketServer has been instantiated, you can assign it to the appDelegate variable.

@main
struct RelayEmulatorApp: App {

   var socketServer : SocketServer

   @NSApplicationDelegateAdaptor(AppDelegate.self) var appDelegate

   func someFunctionThatInstantiatesSocketServer() {
       /// Instantiation for sockectServer is done at this point
       appDelegate.socketServer = socketServer
   }
}

Then you will have access to this instance in AppDelegate class.

class AppDelegate: NSObject, NSApplicationDelegate {

  var socketServer : SocketServer

  func applicationWillTerminate(_ notification: Notification) {
      /// socketServer.close() 
  }

}

Ah, good suggestion. Its much better to inject what is needed as you suggest over me trying to depend on the parent. — Scott, Jun 05 '21 at 16:46

How to access the Swift struct conforming to the App protocol from the AppDelegate

1 Answers1