Socket.io + node : TypeError: Object #<Namespace> has no method

Question

I have a simple JavaScript class like that :

 function MySIOClass(io) { this.io = io this.ns = this.io.of('/notif') this.init() } MySIOClass.prototype.init = function (){ this.ns.on('connection', this.newClient) } MySIOClass.prototype.newClient = function (socket) { socket.on('msg', function (data){ this.handle_msg(data)}) 

}

 MySIOClass.prototype.handle_msg = function (data) { // handle my message } 

I get stuck on the function newClient , each time a socket.io client send an event 'msg', the console triggers

TypeError: Object # <Socket> has no method 'handle_msg'

I tried to keep a reference of the operator this inside the function newClient like that :

 MySIOClass.prototype.newClient = function (socket) { var c = this; socket.on('msg', function (data){ c.handle_msg(data)}) 

}

But no luck too, i got the following error about namespace :

TypeError: Object # <Namespace> has no method 'handle_msg'

My class is exported via a module, everything works except when i try to add a listener with the on method of socket.io inside a class. I have correctly used the "new" operator when i instantiated my class.

Could you help me figure out what's happening ? i tried several things, but none of them worked.

Thanks for your time.

Answer 1

When you pass this.newClient to .on('connection', ...) , you are passing just the function itself and losing the ( this ) context. You need to either create a wrapper function that can access the correct context to call newClient() properly or create a bound version of newClient .

First option:

MySIOClass.prototype.init = function (){
  var self = this;
  this.ns.on('connection', function(socket) {
    self.newClient(socket);
  });
}

Second option:

MySIOClass.prototype.init = function (){
  this.ns.on('connection', this.newClient.bind(this));
}

Regarding the error inside newClient() itself, you are correct in that you have to use a "self"/"that" variable that you can use to access the correct context to call handle_msg() .