Retrieving data from mlab heroku - mongodb

Question

I followed a tutorial to learn Express.js App that performs basic CRUD operations from MongoDB. All operations created locally works fine.
As a next step (not in the tutorial), I needed to integrate mLab provided by Heroku for MongoDB in order to push the app to Heroku.
Now, I need to make necessary changes on the mongoose connection since I am moving from a local database to mLab. I made necessary changes but now the app throws an error.
complaintController.js (class to get request and use the model)
Complaint = require('./complaintModel');
exports.index = function (req, res) {
Complaint.get(function (err, complaints) { //GET function
if (err) {
res.json({
status: "error",
message: err,
});
}
res.json({
status: 200,
message: "Complaints retrieved successfully",
data: complaints
});
});
};
complaintModel.js (local MongoDB this works fine)
var mongoose = require('mongoose');
var complaintSchema = mongoose.Schema({
name: {
type: String,
required: true
},
});
// Export Complaint model
var Complaint = module.exports = mongoose.model('complaint', complaintSchema);
module.exports.get = function (callback, limit) {
Complaint.find(callback).limit(limit);
}
complaintModel.js ( connecting to mLab throws error)
var mongoDB = "MongoDB URI";
var connection = mongoose.createConnection(mongoDB,
{
User: 'username',
Password: 'pass'
});
var Complaint;
connection.on('open', function() {
console.log('connection established!!!');
Complaint = module.exports = connection.model('master_complaint', complaintSchema);
module.exports.get = function (callback, limit) {
Complaint.find(callback).limit(limit);
}
});
Here I get the following error when I give a get request I understood there is an export issue of Complaint Module but any suggestion or idea will be helpful.
TypeError: Complaint.get is not a function
at exports.index (R:\Workings\PersWork\web\webpack-demo\controller\complaintController.js:6:15)
at Layer.handle [as handle_request] (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\layer.js:95:5)
at next (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\route.js:137:13)
at Route.dispatch (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\route.js:112:3)
at Layer.handle [as handle_request] (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\layer.js:95:5)
at R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\index.js:281:22
at Function.process_params (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\index.js:335:12)
at next (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\index.js:275:10)
at Function.handle (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\index.js:174:3)
at router (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\index.js:47:12)
at Layer.handle [as handle_request] (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\layer.js:95:5)
at trim_prefix (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\index.js:317:13)
at R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\index.js:284:7
at Function.process_params (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\index.js:335:12)
at next (R:\Workings\PersWork\web\webpack-demo\node_modules\express\lib\router\index.js:275:10)
at jsonParser (R:\Workings\PersWork\web\webpack-demo\node_modules\body-parser\lib\types\json.js:110:7)

Answer 1

From what I can see in the code. complaintController will be used by the express.js router, Am I correct?
I also see in the complaintModel.js is that the get function you've exported requires 2 parameters which are a filter & a limit. But in the Controller file you're not providing any of those arguments at all.
I haven't tested this myself yet but try changing your complaintModel.js to this
var mongoose = require("mongoose");
var complaintSchema = mongoose.Schema({
name: {
type: String,
required: true
}
});
var Complaint = mongoose.model("master_complaint", complaintSchema);
// Exports the get function
module.exports.get = function(filter, limit, callback) {
var mongoDB = "MongoDB URI";
var connection = mongoose.createConnection(mongoDB, {
User: "username",
Password: "pass"
});
connection.on("open", function() {
console.log("connection established!!!");
Complaint.find(filter)
.limit(limit)
.exec()
.then(results => {
callback(undefined, results)
})
.catch(err => {
console.log(err);
callback("ERROR: Can't query the collection", undefined)
});
});
};
And change the complaintController.js to the following
var Complaint = require("./complaintModel");
module.exports.index = function(req, res) {
var params = req.query;
const filter = params.filter;
const limit = params.limit;
Complaint.get(
filter,
limit,
(err,
complaints => {
if (err) {
res.json({
status: "error",
message: err
});
} else {
res.json({
status: 200,
message: "Complaints retrieved successfully",
data: complaints
});
}
})
);
};