How To Write A Simple Node.js/MongoDB Web Service for an iOS App

[mkatz]

Learn how to create a simple Node.js and MongoDB web service for an iOS app in this tutorial.

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This is a companion discussion topic for the original entry at https://www.raywenderlich.com/2663-how-to-write-a-simple-node-js-mongodb-web-service-for-an-ios-app

[marcosoul]

If you are having an issue with MongoClient.open(), try this code instead:

var url = ‘mongodb://localhost:27017/mongo-server’;
// Use connect method to connect to the server
MongoClient.connect(url, function(error, db) {
if (error) {
console.error(
“Unable to connect to MongoDB. Please make sure mongod is running on %s.”,
url);
process.exit(1);
}

console.log(“Connected to MongoDB successfully.”);
collectionDriver = new CollectionDriver(db);
});

[marcosoul]

If you get bodyParser deprecation error, use the following code instead:

// add the following line to the top of your index.js
var bodyParser = require(‘body-parser’);

// add this following lines after your app.set
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({
extended: true
}));

[marcosoul]

Deprecation may occur if you use res.send(status, body). Instead, just replace those statements with res.status(status).send(body) and it will work fine.

[lawmaestro]

Hi. I’ve gotten to the point in this tutorial where you add an item via:

curl -H “Content-Type: application/json” -X POST -d ‘{“title”:“Hello World”}’ http://localhost:3000/items

However, when I browse to http://localhost:3000/items I’m not seeing any items still. What is the best way to debug this? I’ve added a console log to the app.post(‘/:collection’, function(req, res) function and the code seems to be executing okay.

Any suggestions? Thanks.

[person1]

I got the same error, also not sure what to do. I noticed if you use marcosoul’s code above and opened mongodb in the shell and created a database “mongo-server”, then created a collection “items” and inserted elements into that collection, they would show up, but the save method in the collectionDriver appears to fail. I’m new to this so that’s all I figured out.

[jonchoi]

I’m seeing the same error here as well. @mkatz, would you be able to take a quick look?

(thanks for the awesome tutorial btw!)

[rmathewson]

Also getting the same error.
It’s a shame that I just killed an afternoon getting through this tutorial only for this to happen. How can I use this lesson if I have no confidence that it works???
@rwenderlich , can you help?

[mkatz]

Hi guys, sorry that’s been frustrating. Pretty much the whole stack: iOS/Swift, Javascript, MongoDB, Node.js have all move on quite a bit since this tutorial was written. We’re coming up with a plan on how and when to update this tutorial.

[rmathewson]

Thanks @mkatz.
FWIW I just noticed this error from when I entered the ‘curl’ command in terminal

Could not load page: /items/_id

[btdtphx]

I also had the same error but I changed my package to “mongodb”:“1.4.9”, npm update and It works for me now

[rmathewson]

Hi Michael,
Any developments on this?
Thanks.

[ductrongth95]

If you have any issue with “Error! Exiting… Must start MongoDB first”
That means you didn’t start mongodb yet, use command “cd /usr/local/opt/mongodb/; mongod” to start mongodb.
If you’ve already start mongodb but it still appear that error,
Fix error with this link:
https://www.demainilpleut.fr/dealing-with-the-mongodb-error-datadb-not-found-in-osx/

[ductrongth95]

The reason is that you forgot to add some code from “Updating and Deleting Data” part.

[ductrongth95]

If your delete not only delete id, but also cause end connection of port 3000.
Don’t use “res.status(status).send(body)” as express recommend.
Use “res.sendStatus(status, body)” instead.

[jdewitte]

Hi guys, I’m at the end of the “Using Your Collection Driver” section, and when I run index.js I get:
“js-bson: Failed to load c++ bson extension, using pure JS version
Express server listening on port 3000
Error! Exiting… Must start MongoDB first”

I’ve definitely got mongod running, here’s the output from that:
“2016-08-16T15:41:06.311-0400 I CONTROL [initandlisten] MongoDB starting : pid=79197 port=27017 dbpath=/data/db 64-bit host=jeff-dewitte-mbp
2016-08-16T15:41:06.312-0400 I CONTROL [initandlisten] db version v3.2.8
2016-08-16T15:41:06.312-0400 I CONTROL [initandlisten] git version: ed70e33130c977bda0024c125b56d159573dbaf0
2016-08-16T15:41:06.312-0400 I CONTROL [initandlisten] OpenSSL version: OpenSSL 1.0.2h 3 May 2016
2016-08-16T15:41:06.312-0400 I CONTROL [initandlisten] allocator: system
2016-08-16T15:41:06.312-0400 I CONTROL [initandlisten] modules: none
2016-08-16T15:41:06.312-0400 I CONTROL [initandlisten] build environment:
2016-08-16T15:41:06.312-0400 I CONTROL [initandlisten] distarch: x86_64
2016-08-16T15:41:06.312-0400 I CONTROL [initandlisten] target_arch: x86_64
2016-08-16T15:41:06.312-0400 I CONTROL [initandlisten] options: {}
2016-08-16T15:41:06.313-0400 I - [initandlisten] Detected data files in /data/db created by the ‘wiredTiger’ storage engine, so setting the active storage engine to ‘wiredTiger’.
2016-08-16T15:41:06.313-0400 I STORAGE [initandlisten] wiredtiger_open config: create,cache_size=9G,session_max=20000,eviction=(threads_max=4),config_base=false,statistics=(fast),log=(enabled=true,archive=true,path=journal,compressor=snappy),file_manager=(close_idle_time=100000),checkpoint=(wait=60,log_size=2GB),statistics_log=(wait=0),
2016-08-16T15:41:06.826-0400 I NETWORK [HostnameCanonicalizationWorker] Starting hostname canonicalization worker
2016-08-16T15:41:06.826-0400 I FTDC [initandlisten] Initializing full-time diagnostic data capture with directory ‘/data/db/diagnostic.data’
2016-08-16T15:41:06.828-0400 I NETWORK [initandlisten] waiting for connections on port 27017”

I’ve tried changing the mongodb version in my package.json file to 3.2.8 to match the output from mongod (since this tutorial is a little old), and then I tried 1.4.9 since that helped someone earlier, but no dice. Anyone know what could be going on?

[skykid14]

From btdtphx: “I changed my package to “mongodb”:“1.4.9”, npm update and It works”

I can confirm this fixed the problem for me as well on OSX. Basic steps:

1. stop node.js if running.
2. In package.son, change the mongo dependency to: “mongodb”: “1.4.9”
3. run npm update
4. In a separate terminal, start node.js (“node .” or “node index.js”)
5. Back in your first terminal, send the post request: curl -H “Content-Type: application/json” -X POST -d ‘{“title”: “Hello World”}’ http://localhost:300/items
6. Go to “http://localhost:3000/items” and see the table is now created.

Additional: the older dependency “mongodb”: “1.3.23” does not appear to be compatible with the current mongod daemon. The problem was not with the get, but with the post, which I found by reverting back to 1.3.23 and loading the page from step 6 above and seeing the table with my prior entries. I posted a new entry with step 5 above under the old 1.3.23, then upgraded once again to 1.4.9, restarted node.js and the browser and viola, the new entry appeared in the table.

[skykid14]

This is not your problem: “Failed to load c++ bson extension, using pure JS version”. Basically mongoDB requires BSON 0.2.12, which on OSX has nothing in its build/release directory. The error is produced by “node_modules/bson/ext/index.js”. There you can see the reason is that index.js can’t find the “bson” file/directory in its build/release subfolder. You can get the error to go away by simply copying lib/bson/bson.js (or browser_build/bson.js) into /build/release. It’s a hokey fix. And it’s not even necessary, as you’ll see in index.js, the very next action taken is to load up the bson.js file from lib/bson/bson.js

As to your error, when you installed mongodb, the author “mkatz” told you to note (copy) the summary that was spit out by “brew install mongodb”. In my case, I got a message in terminal saying “Or, if you don’t want/need a background service you can just run:
mongod --config /usr/local/etc/mongod.conf”. Starting the mongod daemon with this line works for me. To note: trying to start it by just calling “mongod” produces an error similar to yours. Remember if you’re changing your package.json file to depend on mongo 1.4.9, you’ll need to run “npm update” to actually install it to you project folder.

[skykid14]

In collectionDriver.js, calling “remove” does not return the removed document. It returns the number of documents removed. This is probably remove() was altered when I updated mongo from 1.3.23 to 1.4.9 in package.json. In order to return the removed object, you must “get” it from the DB prior to the delete, then return it in the callback in place of “doc”.

I’ve rewritten CollectionDriver.prototype.delete as follows:

CollectionDriver.prototype.delete = function(collectionName, entityId, callback) {
var self = this;
this.getCollection(collectionName, function(error, the_collection) { //A
if (error) callback(error);
else {
self.get(collectionName, entityId, function(error, objs){
var objectToDelete = objs;
if (error) callback(error);
else {
the_collection.remove({‘_id’:ObjectID(entityId)}, function(error,doc) { //B
var doc_string = "DOCS REMOVED: " + doc;
console.log(doc_string); //sent to SERVER CONSOLE
if (error) callback(error);
else callback(null, objectToDelete);
});
}
});
}
});
};

[billionssg]

thx, it solved mine too