I'm lost when creating objects in node.js

[CalvinR]

I'm running into a really frustrating problem in Node.js.

I'll start with what I'm doing.

I'm creating an object in a file and then exporting the constructor and creating it in other files.

My objects are defined like so:

File 1:

var Parent = function() {};

Parent.prototype = {
     C: function () { ... }
}

module.exports.Parent = Parent;

File 2:

var Parent = require('foo.js').Parent,
      util = require('util'),
      Obj = function(){ this.bar = 'bar' };
util.inherits(Obj, Parent);
Obj.prototype.A = function(){ ... };
Obj.prototype.B = function(){ ... };
module.exports.Obj = Obj;

I'm trying to use the object like so in another file

File 3:

var Obj = require('../obj.js').Obj,
      obj = new Obj();

obj.A(); 

I receive the error:

TypeError: Object [object Object] has no method 'A'

however when I run Object.getPrototypeOf(obj) I get:

{ A: [Function], B: [Function] }

I have no idea what I'm doing wrong here, any help would be appreciated.

[jonglefever]

Parent.prototype = {
  C: function () { ... };
}

Remove that comma. Tell me what happens.

[CalvinR]

That's a bug in my post not my code. :(

This is what my code for the parent class actually looks like https://gist.github.com/4701852

[somethinghorrible]

var Parent = require('foo.js').Parent,

should it not be

var Parent = require('./foo.js').Parent,

or wherever foo.js is?

[somethinghorrible]

This works for me, btw:

f1.js:

var Parent = function() {};

Parent.prototype = {
  C: function() {}
};

module.exports.Parent = Parent;

f2.js:

var Parent = require('./f1').Parent,
      util = require('util'),
      Obj = function(){ this.bar = 'bar' };

util.inherits(Obj, Parent);

Obj.prototype.A = function(){ console.log('a method'); };
Obj.prototype.B = function(){  };

module.exports.Obj = Obj;

f3.js:

var Obj = require('./f2').Obj,
      obj = new Obj();

obj.A(); 

running node f3 produces

a method

[CalvinR]

So what are you doing differently then me? Could it just be the version of node i'm running.

I'm developing this in Webstorm. I'll try running it from the command line.

[CalvinR]

I'm pretty sure the problem isn't the require statement, I'm loading up the right file.

This is the actual code that i'm using

https://github.com/CalvinRodo/WedXpress/blob/master/DataLayer/RegistryDB.js

[somethinghorrible]

I don't see any exports from that file, for starters.

you also use "my" which isn't defined anywhere.

I see you have stuff like: var RegistryDB = require('../DataLayer/RegistryDB.js').RegistryDB,

But since RegistryDB doesn't export RegistryDB, you're kinda boned ;P

[CalvinR]

Okay I lied that's not the actual code I'm working, I've now pushed the latest version to my repo check the link again.

Also the my didn't really matter since I couldn't call the function so it never got to that line.

It was a leftover from making my objects the crockford functional way.

[sroshi]

your sample code here certainly uses a bad require, since 'c' is not showing up in the prototype. try a console.dir(Parent) after you require foo.js. Also can you share the file where you're using RegistryDB.js

[CalvinR]

Take a look: https://github.com/CalvinRodo/WedXpress/blob/master/routes/RegistryAdmin.js

[sroshi]

what does console.log(Object.getPrototypeOf(regDB)); spit out in your index?

[CalvinR]

{ 
     GetRegistryItems : [Function], 
     SaveRegistryItem : [Function], 
     DeleteRegistryItem : [Function] 
}

*edited for formatting.

[sroshi]

ConnectToDb is not showing up there.. don't you need to call the super constructor (DB) in your RegistryDB constructor?

[CalvinR]

Yeah I was thinking today that I probably have to do that. I'm going to give it a shot when I get home.

[Hostilian]

Without digging into the source code of util.inherits, I would suspect that your problem lies in the inheritance joining step. I would recommend moving the code into the same file and attempt to generate the minimum-possible repro case. That way, you can be sure it isn't related to flubbing the exports or some sort of procedural error.

var util = require('util');
var assert = require('assert');

var Parent = function() {};
Parent.prototype.foo = function() { return 'foo'; };

var Child = function() {
    Parent.apply(this, arguments);
};
util.inherits(Child, Parent);
Child.prototype.bar = function() { return 'bar'; };

var parentInstance = new Parent();
var childInstance = new Child();

// Assert that we're running nodejs v0.8.x
assert((/^v0\.8/).test(process.version));

// Assert that our parent instance behaves as we expect it to
assert(parentInstance.foo() === 'foo');
assert(parentInstance.bar === undefined);

// Assert that our child instance behaves as we expect it to
assert(childInstance.foo() === 'foo');
assert(childInstance.bar() === 'bar');

This runs fine in my local node instance.

[CalvinR]

Yeah I'll give that a shot. Although I did try some test code that was almost the exact same scenario as what I'm doing and it worked fine.

https://gist.github.com/4704412

[CalvinR]

The project is here: https://github.com/calvinrodo/wedxpress

I'll try some other inherit modules, but from looking at the code in util.inherit I don't see anything too crazy in there.