node.js/express js interaction between model and controller

Question

I am new to node.js so please bear with me.

I am wondering what is the proper way to pass the model to the controller in node. I sort of having it working but when I call a method from the model in my controller what I have returning from the model is 'undefined' and I am not sure why. My connection to the DB is fine. Take a look at my files and see my comments in all caps.

routes.js

module.exports = function(app, dbConnection) {
 var theIndexModel = require('../models/index.server.models')(dbConnection);
 var index = require('../controllers/index.server.controller')(theIndexModel);

 app.get('/', index.homePage);
};

models.js

function IndexModel(dbConnection) {

  modelMethods = {};

  modelMethods.getAllUsers = function(req, res) {
      var query = "SELECT * FROM `users`";
      dbConnection.query(query, function(err, rows, fields) {
        return rows; //NOT RETURNING ANYTHING WHEN I CALL FROM CONTOLLER!!
      });
  };

 return modelMethods;
}

module.exports = IndexModel;

controller.js

function IndexController(theIndexModel) {
  controllerMethods = {};
  controllerMethods.homePage = function(req, res) {
    console.log(theIndexModel.getAllUsers()); //UNDEFINED HERE, WHEN I SHOULD BE GETTING USERS FROM THE DB
    res.render('index', {
        title: 'hello'
    });
  };


// Return the object that holds the methods.
return controllerMethods;
}

module.exports = IndexController;

What am I doing wrong? Thanks in advance.

welcome to the world of asynchronous programming. theIndexModel.getAllUsers() is actually returning undefined. the callback passed into dbConnection.query is receiving the rows. — NG.
– NG., Commented Jan 18, 2016 at 23:09

iagowp · Accepted Answer · 2016-01-18 23:22:15Z

1

As pointed by NG, your problem is with asyc code. return rows is returning the rows, only you are never catching it.

To fix this, you can learn about promises, or dive into callback hell.

If you choose the callback hell, it will look something like this:

controller.js

function IndexController(theIndexModel) {
  controllerMethods = {};
  controllerMethods.homePage = function(req, res) {
   theIndexModel.getAllUsers(function(err, rows, fields){
     res.render('index', {
        title: 'hello,
        users: rows
     });
   });

  };


// Return the object that holds the methods.
return controllerMethods;
}

module.exports = IndexController;

and models.js

function IndexModel(dbConnection) {

  modelMethods = {};

  modelMethods.getAllUsers = function(cb) {
      var query = "SELECT * FROM `users`";
      dbConnection.query(query, cb);
  };

 return modelMethods;
}

module.exports = IndexModel;

answered Jan 18, 2016 at 23:22

iagowp

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5 Comments

John Over a year ago

Thanks for responding, I tried what you suggested but I'm still getting 'undefined'

John Over a year ago

when I log 'rows' in getAllUsers its undefined.

iagowp Over a year ago

like this? getAllUsers(function(err, rows, fields){ console.log(rows) }

iagowp Over a year ago

Just to make sure, you are getting undefined inside the controller, when you invoke getAllUsers, inside the function you pass as a callback?

John Over a year ago

I had an error in another file... my mistake. Now it is working. Thanks dude!

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