我怎样才能获得Node.js类和socket.io事件上下文？

Question

I have a Problem with the correct context in a JavaScript class and a socket.io 'disconnect' event.

My class looks like so:

class GameSession {

   constructor(gameSessionId) {
       this._gameSessionId = gameSessionId;
       this._players = new Map();
   }

   addPlayer(socketId,player) {
       this._players.set(socketId,player);
       this.addListeners(player);
   }

   addListeners(player) {
       player.socket.on('disconnect',this.playerLeave);
   }

   playerLeave () {
       // ##### here is my Problem
   }
}

In the "playerLeave" function I can access the socket id with "this.id". But to access the "_players" map I need the context of the class which I get if I change the "addListeners" function to:

addListeners(player) {
    player.socket.on('disconnect',() => this.playerLeave());
}

But by this I loose the context of the Event and so the possebility to call "this.id" to receive the socket id.

How can I get both?

Answer 1

Can you try with something like this:

addListeners(player) {
  player.socket.on('disconnect', this.playerLeave.bind(this));
}

playerLeave (socket) {...}

Answer 2

I was facing the same issue, and I found a solution. (I hope you found it too!)

You just have to bind both of instances like this:

   addListeners(player) {
       var playerSocket = player.socket;
       playerSocket.on('disconnect',this.playerLeave.bind(playerSocket, this));
   }

And the class instance will be passed as a parameter in your socketIO event :

   playerLeave(gameSessionInstance) {
       console.log('Bye '+this.id);
       gameSessionInstance.removePlayer(this.id); // if you have a method called removePlayer for example
   }