Rethinkdb changesfeed in Express.js using thinky

Question

Created a basic express.js application and added a model (using thinky and rethinkdb) trying to pass the changesfeed to the jade file and unable to figure how to pass the results of the feed. My understanding is that changes() returns infinite cursor. So it is always waiting for new data. How to handle that in express res. Any idea what am I missing here?

    var express = require('express');
var router = express.Router();
var thinky = require('thinky')();
var type = thinky.type;
var r = thinky.r;

var User = thinky.createModel('User', {
    name: type.string()   
});
//end of thinky code to create the model


// GET home page. 
router.get('/', function (req, res) {
    var user = new User({name: req.query.author});
    user.save().then(function(result) {      
        console.log(result);
    });
    //User.run().then(function (result) {
        //res.render('index', { title: 'Express', result: result });
    //});
    User.changes().then(function (feed) {
        feed.each(function (err, doc) { console.log(doc);}); //pass doc to the res
        res.render('index', { title: 'Express', doc: doc}) //doc is undefined when I run the application. Why?
    });
    });
module.exports = router;

Mohammad Ali · Accepted Answer · 2017-02-16T02:45:51.380

1

The problem that I believe you are facing is that feed.eachis a loop that is calling the contained function for each item contained in the feed. So to access the doc contained in console.log(doc) you are going to need to either place your code in the function in which doc exists(is in the scope of the variable doc), or you are going to need to make a global variable to store doc value(s).

So for example, assuming doc is a string and that you wish to place all doc's in an array. You would need to start off by creating a variable which has a scope that res.render is in, which for this example will be MYDOCS. Then you would need to append each doc to it, and after that you would simply use MYDOC anytime you are attempting to access a doc outside of the feed.each function.

var MYDOCS=[];
User.changes().then(function (feed){
    feed.each(function (err, doc) { MYDOCS.push(doc)});
});
router.get('/', function (req, res) {
    var user = new User({name: req.query.author});
    user.save().then(function(result) {      
        console.log(result);
    });
    //User.run().then(function (result) {
        //res.render('index', { title: 'Express', result: result });
    //});
        res.render('index', { title: 'Express', doc: MYDOCS[0]}) //doc is undefined when I run the application. Why?
    });
module.exports = router;

edited Feb 16 '17 at 02:45

answered Feb 15 '17 at 22:37

Mohammad Ali

878
8
16

Hi Mohammad, I appreciate taking the time to answer my question but it didn't work. doc still undefined. I'll have to look at integrating socket.io to pass it to the front. I hope Express.js next version will think about real time updates from the db. It is an important feature that every new framework should consider. – Marco Feb 16 '17 at 01:46
@marco If you add console.log MYDOCS right before res.render do you get an output? – Mohammad Ali Feb 16 '17 at 01:48
Yes. But that is the same issue I had before. – Marco Feb 16 '17 at 01:58
I think i may have misinterpreted the question. Are you attempting to add all changes for the life of the application to res? or just the changes that occur during the page request? – Mohammad Ali Feb 16 '17 at 02:37
Yes, the life of the application (live updates to be pushed to the user dashboard) not during the page request. My fault. Didn't explain the end goal. – Marco Feb 16 '17 at 02:40
I have edited my answer to reflect your clarification of the question, if the code above does not work please be as descriptive of the problem as possible, thank you for your time – Mohammad Ali Feb 16 '17 at 02:47
Works. Thanks. So you create the global var and assign the output to it. – Marco Feb 16 '17 at 03:23

Rethinkdb changesfeed in Express.js using thinky

1 Answers1