Pass configuration to controller

Question

I am building a node.js app that will upload files to my S3 bucket using knox. I am able to interact with S3 as expected, but I would like to make my controller to receive configuration so I can dynamically construct my client with configuration values.

My questions is how do I get configuration paramters down the call stack to my controller without being careless?

Disclaimer: I am rather new to Node.js so it could be simply my lack of knowledge in the difference between exports. and module.exports.*

Here is an example of how the interaction works with my code:

app.js

...
config = require('./config/config')['env'];
require('./config/router')(app, config);
...

router.js

module.exports = function(app, config) {
...
  var controller = require('../app/controllers/home'); //Is there a way for me to pass config here?
  app.post('/upload', controller.upload); //Or here?
...
}

home.js

var knox = require('knox');

var client = knox.createClient({ ... }); //I want to use config.key, config.secret, etc instead of hard-coded values
...
exports.upload = function(req, res) {
  //Use client
}
...

Ethnology

Answer 1

Try doing something like this...

var config = require('./config/config')['env'];

// The use function will be called before your 
//  action, because it is registered first.
app.use(function (req, res, next) {

  // Assign the config to the req object
  req.config = config;

  // Call the next function in the pipeline (your controller actions).
  return next();

});

// After app.use you register your controller action
app.post('/upload', controller.upload); 

And then in your controller action...

exports.upload = function(req, res) {

  //Your config should be here...
  console.log(req.config);

}

Ps. I can not try it right now, but I solved a similar issue like this.

Eighteenth

I have a cluster of Node.js worker processes, each running an Express server instance and I used this answer to pass a worker ID into the request handlers for each request. This helps with things like generating unique IDs and logging. – Cila

Answer 2

You can pass the configuration in as a parameter to you controller

Controller

// controller.js file
module.exports = function(req, res, config) {
  console.log('config parameter passed to controller', config);
  res.end('config passed')
}

App

// index.js file with the express app
var controller = require('./controller');
var config = {
  key1: 'foo'
};
var express = require('express');
var app = express();
var port = 3000;
app.get('/', function(req, res){
  controller(req, res, config);
});
app.listen(port);

console.log('app listening on port', 3000);

Demo

You can check out the github repo for a complete example

Hawn

Thanks for the answer. The problem is this is all in one file. My desire was to keep things separate thus my problem. Bart's approach got me where I needed to be. – Ethnology

Answer 3

Alternative approach if you want to call multiple functions from one single route, this will do it.

Route

var users = require('../controllers/users');
 app.route('/login').post(function(req, res){
   if(users.authenticate()){
     console.log('valid user');
     if(users.createUser())
     {
       console.log('user created');
     }
   }
});

Controller

exports.authenticate = function(req, res, next) {
   return true;
};
exports.createUser = function(req, res, next) {
   return true;
};

Martens