Node.js eventEmitter + http.request

Question

I made this tutorial node.js eventEmitter , it worked beautifully. I added a method that uses http.request to get data that works and emits data.

the problem is that the listener did not catch the event!

can anyone help?

the 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

It’s hard to determine ...

The problem is the pointer thisfrom this.emit("tweets", tweets);. You make this call from an anonymous callback passed to response.on, therefore thisdoes not represent the object Eventeryou created. To solve this problem, you need to “save” the pointer this(common practice).

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