TypeError：对象函数...没有'on'方法

Question

I am new to node.js and trying to create my first module. But i am getting an error

TypeError: Object function SetAstAppLog.....has no method 'on'

My module file contains following code :

var EventEmitter = require('events').EventEmitter;
var util = require('util');
module.exports = SetAstAppLog;  
util.inherits(SetAstAppLog, EventEmitter);    

function SetAstAppLog(logFolderPath,fileNamePrefix,fileSize,logStreamObject) {
    EventEmitter.call(this);
.
.
.
.
    this.emit('objCreated');
}

and in app.js i am doing following things :

var SetAstAppLog = require('astAppLog');
var fileSize = 1024;

SetAstAppLog.on('objCreated', function () {
    console.log('an object was created');
});

SetAstAppLog.on('written', function () {
    console.log('Write operation completed.');
});

var objCommLogger = new SetAstAppLog(logFolderPath,logCommFilePrefix,fileSize,logCommMsg);
var objErrorLogger = new SetAstAppLog(logFolderPath,logErrorFilePrefix,fileSize,logErrorMsg);

Here, i am using node js with v0.10.21.
I am not able to find out why i am getting this error even my module file contains EventEmitter
Can anyone help to solve this issue?

Answer 1

You are exporting the function without calling it. You need to call it:

var SetAstAppLog = require('astAppLog')();

Edit: I failed to notice that you called the function lower in your script. You should be attaching the event handlers to the instances, not the constructor.

var objCommLogger = new SetAstAppLog(logFolderPath, logCommFilePrefix, fileSize, logCommMsg);
objCommLogger.on(...);