Accessing subscribed topics on socket close event

[tayler-king]

I've previously been tracking topics that individual sockets subscribe to manually, creating a list for each socket.

I felt that this was unnecessary seeing as though you can call socket.getTopics() to retrieve a list of subscribed topics.

On the socket close event I'd like to do some clean-up, namely retrieving the list of topics the disconnected socket has ben subscribed to. An example of this would be:

uWS.App().ws('/socket', {
  close: socket => emitter.emit('closed', socket)
});

emitter.on('closed', socket => {
  const topics = socket.getTopics();

  topics.forEach(topic => {
    // do something here
  });
});

Unfortunately when attempting to call socket.getTopics() in the above scenario, I'm experiencing the error Invalid access of closed uWS.WebSocket/SSLWebSocket.

Is calling socket.getTopics() after the close event fires undefined behaviour, or is this an issue due to how the event loop is handling the emitter callback? I'm still able to access socket data in the emitter's event callback, just not call getTopics.

Documentation states "You may not use WebSocket after this event.", so I'm lead to believe that the above would be undefined behaviour. In that case, is there a better solution to what I'm wanting to implement other than keeping track of subscribed topics manually?

[e3dio]

uWS.App().ws('/socket', {
  close: socket => {
    socket.topics = socket.getTopics();
    emitter.emit('closed', socket);
  }
});

emitter.on('closed', socket => {
  socket.topics.forEach(topic => {
    // do something here
  });
});

[uNetworkingAB]

See https://github.com/uNetworking/uWebSockets/releases/tag/v20.32.0

[tayler-king]

Thanks. Seems like the sensible way to do it.