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Streaming Geo Coordinates API From MongoDB: iOS App

5 min read • Stephen Blum on May 3, 2013

**NOTE: Since we wrote this tutorial, we’ve released a new, completely-redesigned version of our iOS SDK (4.0). We rebuilt the entire codebase and took advantage of new features from Apple, simplifying and streamlining the SDK.

The code from this tutorial still works great, but we recommend checking out our new SDK. We’ve included a migration guide to help you move from 3.x to 4.0, and a getting started guide to help you create a simple Hello World application in minutes.**

Not long ago we partnered with a high-standards online engineering broker (an online listing service where you can post engineering projects). The partnership involved joint PR and blogging, however a new opportunity/idea was presented. This particular idea stemmed from a commission listed on the broker’s website which listed requirements for building an integrated Real-time Map Service. We took the opportunity and built a Ruby GEM with a sprinkle of documentation and HTML5.

geo coordinates api

Geo Coordinates Quick Start Guide

For those of you who need a quick

mini-guide to getting your MongoDB installed and running with data sync streaming directly to your mobile app, you can follow this guide: MongoDB Pipe GitHub Repository. It will show you how to download/install MongoDB and the MongoPipe GEM.

Real-time Data Stream of Geo Coordinates

Lat/Long from MongoDB replicated to your iPhone App

The commission at the online workplace was posted as a $3,025 bounty. Rather than taking the commission for ourselves, which involves building and delivering the solution in a private exchange, we instead reviewed the specifications and requirements and we developed an open source implementation that you can download and run for your live app today! MIT License, so you can use this however you desire. We even created a GEM for you and made it easy to get started:

gem install monogopipe

Downloading the GEM is the first step in the process and next we’ll walk you through more details.

  1. Installing the Ruby gem and
  2. Executing the commands to setup MongoDB and
  3. Running the Pipe Daemon.
  4. Launching the Map Viewer.
  5. Finally inserting lat/long coords into MongoDB.
  6. Result is live-animated points on a map displayed on the iPhone.

Usage of the MongoPubNubPipe gem and source code is available via GitHub if you want to see everything –MongoDB Pipe GitHub Repository

This becomes the new interface that is available with mongopipe gem:

MongoPubNubPipe::Connect.new(...)

Usage of MongoPubNubPipe is available lower in this document.

MongoDB Geo Coordinates

This application code and gem library will provide you a way to easily add a live always-on map connection which allows you to send lat/long signals directly to the device displaying the map with the specific Lat/Long DB written into MongoDB. This will cause the device to draw an animated dot onto the screen of the device in real time.

The dot that animates is triggered by simply writing to your MongoDB collection directly either through the mongo console or through your RoR/Ruby Server Code. For example here is a MongoDB Console Command that will cause a DB write, creating a Document, which then triggers the sync with the consumer iPhone device that is rendering the map in real time.

db.collection_name.insert({ latlon : [ 1.5, 2.0 ] })

Once you’ve written a Lat/Long coordinate into MongoDB collection, the process begins instantly synchronizing with any connected iPhone. We where able to include several feature requests and here follows the requirements:

  • When a new Lat/Lon document is inserted into MongoDB, stream the Lat/Lon data to a mobile device is push data.
  • Use a Ruby or Node.JS Service to stream the data out of MongoDB as it is written in real time.

Simple enough, yes, though it requires moving pieces. We simplified the process and built two modules: one in Ruby and one in HTML5. We’ll walk through the methods for getting you started and how to hook into the stream on your iPhone App. You can fast-track the tutorial and go strait to the GitHub Repository or gem install mongopipe package for ruby.

GitHub Repository

MongoDB Pipe GitHub Repository

gem install monogopipe

How it Works

MongoPipe is a new tool powered by PubNub that streams your MongoDB Documents from your MongoDB Collection directly to your iPhone App in less than 0.25 seconds (real-time) using the PubNub Data Stream Network. Your iPhone app opens an always-on TCP Socket Connection to PubNub while a dispatch process runs on your MongoDB server via Tailable Cursors to catch inserted documents. The data is streamed and brokered via PubNub Network directly to your iPhone App in real time.

MongoDB Tailable Cursors

The ruby GEM mongopipe utilizes the tailable cursor interface provided by MongoDB Core. Document Data is then piped directly through the PubNub Network which uses a direct broadcast synchronization socket with the mobile app.

Next we’ll show you what the process is to get the mongopipe running on your Ruby Server.

Make sure MongoDB is running

mongod

Next open a text editor and copy/paste the following mongopipe example.

require 'rubygems'
require 'mongopipe'
## ------------------------------------------------------------------------
## Pipe MongoDB for Inserts
## ------------------------------------------------------------------------
MongoPubNubPipe::Connect.new(
    :puts_usage    => true,
    :publish_key   => 'demo',
    :subscribe_key => 'demo',
    :db            => 'test',
    :collection    => 'cap_collection',
    :callback      => lambda{ |doc|
        ## Optional Callback Called on Doc Insert
        ## Remove :callback if you don't need it.
        puts(doc)
    }
).pipe()

Save this to a file pipe.rb for example then execute it.

ruby pipe.rb

This will connect directly to MongoDB and print usage guide on next steps. Here is a sample output of what may be provided via the puts(doc) output:

Step 1: Open Your Browser to Show PubNub Pipe Console
> open https://www.pubnub.com/console?channel=test.cap_collection 
Step 2: Open Demo Map on Your Phone 
> open http://goo.gl/HAqAv#test.cap_collection 
Step 3: Insert Test Data 
> ./mongo
> use test
> db.cap_collection.insert({ latlon : [ 1.5, 2.0 ] })

Remaining Details

This blog entry was intended to give you a quick skim over the details on how the mongopipe ruby gem works and what is involved in coordinating the embeddable mobile HTML5 animated map.

If you have any more questions please tweet @PubNub directly.

You may be curious about the connectivity mechanism between your iPhone App and your MongoDB Sever. Checkout the PubNub WebSocket Reference below to see the transport mechanism utilized.

Thank you for reading!

PubNub WebSocket Reference

The MongoDB Pipe uses the PubNub Network WebSocket interface which provides an always-on socket connection to your iPhone app. The PubNub Network WebSocket acts as a broadcast receiver and syncs directly to your mobile device in real time from your MongoDB server via MongoPipe.

Following is an example of how the Map app implements the socket:

// Create Socket Connection
var socket = new WebSocket(
    'wss://pubsub.pubnub.com/PUBLISH_KEY/SUBSCRIBE_KEY/CHANNEL'
);
// Set Message Receiver Function
socket.onmessage = receiver;
// Receiver Function Prints Data Result
function receiver(evt) { console.log(evt.data); }

geo coordinates api

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