node.js eventEmitter + http.request

Question

i did this tutorial node.js eventEmitter, it worked nicely. I added a method that uses http.request to get data, which works and emit the data.

the problem is that the listener doesn't catch the event !

can someone help ?

code :

var events = require('events');
var util = require('util');
var http = require('http');

//http request options, it query the twitter api and get the public timeline, works!
var options = {
    hostname : 'api.twitter.com',
    port : 80,
    method : 'get',
    path : '/1/statuses/public_timeline.json?count=3&include_entities=true'
}

// The Thing That Emits Event
Eventer = function(){
  events.EventEmitter.call(this);

//tutorial examples
  this.kapow = function(){
    var data = "BATMAN"
    this.emit('blamo', data);
  }

//tutorial examples
  this.bam = function(){
     this.emit("boom");
  }

//my method
  this.GetTweetList = function(){
    var tweets = "";
        var req = http.request(options, function(response){
                    var body = "";
                    response.on('data',function(data){
                        body += data;
                    });
                    response.on('end', function(){
                        tweets = JSON.parse(body);
                        this.emit("tweets", tweets);
                        util.puts('!!!!!!!!!! got some data !!!!!!!!!! \n');
                    });
                });
        req.end();
    }
 };
util.inherits(Eventer, events.EventEmitter);

// The thing that listens to, and handles, those events
Listener = function(){

//tutorial examples
this.blamoHandler =  function(data){
    console.log("** blamo event handled");
    console.log(data);
  },

//tutorial examples
  this.boomHandler = function(data){
    console.log("** boom event handled");
  }

//my listener method
  this.GetTweetListHandler = function(data){
        console.log("** tweets event handled");
        util.put(data);
        util.puts('!!!!!!!!!! got some data in listener !!!!!!!!!! \n');

    }

};

// The thing that drives the two.
//instanciating the object and liking the methodes
var eventer = new Eventer();
var listener = new Listener(eventer);
eventer.on('blamo', listener.blamoHandler);
eventer.on('boom', listener.boomHandler);
eventer.on('tweets', listener.GetTweetListHandler);


//calling the methodes
eventer.kapow();//works
eventer.bam();//works
setInterval(eventer.GetTweetList, 2000);
//eventer.GetTweetList();// still waiting but the eventer display that he got the data

Answer 1

Hard one to spot ...

The problem is the this pointer from this.emit("tweets", tweets);. You are doing this call from within an anonymous callback passed to response.on, so this does not represent the Eventer object that you created. To solve it, you need to "save" the this pointer (a common practice).

var tweets = "";
var self = this;
....
self.emit("tweets", tweets);