Helios - an extensible open source mobile backend framework

Helios is an open-source framework that provides essential backend services for iOS apps, from data synchronization and user accounts to push notifications, in-app purchases, and passbook integration. It allows developers to get a client-server app up-and-running in just a few minutes, and seamlessly incorporate functionality as necessary.

Helios is designed for "mobile first" development. Build out great features on the device, and implement the server-side components as necessary. Pour all of your energy into crafting a great user experience, rather than getting mired down with the backend.

One great example of this philosophy in Helios is Core Data Synchronization. This allows you to use your existing Core Data model definition to automatically generate a REST webservice, which can be used to shuttle data between the server and client. No iCloud, no problem.

Helios Web UI Screenshot

Helios also comes with a Web UI. Browse and search through all of your database records, push notification registrations, in-app purchases, and passbook passes. You can even send targeted push notifications right from the browser.

Requirements

  • Ruby 1.9
  • PostgreSQL 9.1 (Postgres.app is the easiest way to get a Postgres server running on your Mac)

Getting Started on OS X

  1. Verify Ruby Installation:

    $ ruby -v

If you do not see ruby 1.9.x printed, we suggest installing RVM to manage Ruby versions.

  1. Install Helios at the command prompt:

    $ gem install helios

  2. Create a new Helios application:

    $ helios new myapp

  3. Create a Postgres database at the command prompt:

    $ createdb -h localhost myapp

Database credentials are read from the .env file generated by Helios, as the variable DATABASE_URL. By default, this will point to a database with the name of the generated app.

  1. Change directory to myapp

    $ cd myapp

  2. Start the web server:

    $ helios server

  3. Go to http://localhost:5000/admin and you’ll see your app's Web UI

Read on for instructions on the following:

  • Linking a Core Data model
  • Integrating Helios into your mobile client

Usage

Built on the Rack webserver interface, Helios can be easily added into any existing Rails or Sinatra application as middleware. Or, if you're starting with a Helios application, you can build a new Rails or Sinatra application on top of it.

This means that you can develop your application using the tools and frameworks you love, and maintain flexibility with your architecture as your needs evolve.

Sinatra / Rack

Gemfile

gem 'helios'

config.ru

require 'bundler'
Bundler.require

run Helios::Application.new do
  service :data, model: 'path/to/DataModel.xcdatamodel'
  service :push_notification, apn_certificate: 'path/to/apple_push_notification.pem', apn_environment: 'development'
  service :in_app_purchase
  service :passbook
end

Rails

To create a Rails app that uses Postgres as its database, pass the -d postgresql argument to the rails new command:

$ rails new APP_PATH -d postgresql

If you're adding Helios to an existing Rails project, be sure to specify a PostgreSQL database in config/database.yml and check that the pg gem is included in your Gemfile:

Gemfile

gem 'helios'
gem 'pg'

Helios can be run as Rails middleware by adding this to the configuration block in config/application.rb

config/application.rb

config.middleware.use Helios::Application do
  service :data, model: 'path/to/DataModel.xcdatamodel'
  service :push_notification, apn_certificate: 'path/to/apple_push_notification.pem', apn_environment: 'development'
  service :in_app_purchase
  service :passbook
end

Available Services

Each service in Helios can be enabled and configured separately:

data: Generates a REST webservice from a schema definition. Currently supports Core Data (.xcdatamodel) files.

Parameters

  • model: Path to the data model file

Associated Classes

Each entity in the specified data model will have a Sequel::Model subclass created for it under the Rack::CoreData::Models namespace.

Endpoints
GET /:resources Get list of all of the specified resources
POST /:resources Create a new instance of the specified resource
GET /:resources/:id Get the specified resource instance
PUT /:resources/:id Update the specified resource instance
DELETE /:resources/:id Delete the specified resource instance

push_notification: Adds iOS push notification registration / unregistration endpoints.

Associated Classes

  • Rack::PushNotification::Device
Endpoints
PUT /devices/:token Register or update existing device for push notifications
DELETE /devices/:token Unregister a device from receiving push notifications
POST /message Send out a push notification to some devices

in_app_purchase: Adds an endpoint for iOS in-app purchase receipt verification endpoints, as well one for returning product identifiers.

Associated Classes

  • Rack::InAppPurchase::Receipt
  • Rack::InAppPurchase::Product
Endpoints
POST /receipts/verify Decode the associated Base64-encoded receipt-data, recording the receipt data and verifying the information with Apple
GET /products/identifiers Return an array of valid product identifiers

passbook: Adds endpoints for the web service protocol for communicating with Passbook

Associated Classes

  • Rack::Passbook::Pass
  • Rack::Passbook::Registration
Endpoints
GET /v1/passes/:passTypeIdentifier/:serialNumber Get the Latest Version of a Pass
GET /v1/devices/:deviceLibraryIdentifier/registrations/:passTypeIdentifier[?passesUpdatedSince=tag] Get the Serial Numbers for Passes Associated with a Device
POST /v1/devices/:deviceLibraryIdentifier/registrations/:passTypeIdentifier/:serialNumber Register a Device to Receive Push Notifications for a Pass
DELETE /v1/devices/:deviceLibraryIdentifier/registrations/:passTypeIdentifier/:serialNumber Unregister a Device

Command-Line Interface

Helios comes with a CLI to help create and manage your application. After you $ gem install helios, you'll have the helios binary available.

$ helios --help
helios

A command-line interface for building mobile infrastructures

Commands:
  console              Open IRB session with Helios environment
  help                 Display global or [command] help documentation.
  link                 Links a Core Data model
  new                  Creates a new Helios project
  server               Start running Helios locally

Creating an Application

The first step to using Helios is to create a new application. This can be done with the $ helios new command, which should be familiar if you've ever used Rails.

$ helios new --help

Usage: helios new path/to/app

  The `helios new` command creates a new Helios application with a default
directory structure and configuration at the path you specify.

Options:
  --skip-gemfile       Don't create a Gemfile
  -B, --skip-bundle    Don't run bundle install
  -G, --skip-git       Don't create a git repository
  --edge               Setup the application with Gemfile pointing to Helios repository
  -f, --force          Overwrite files that already exist
  -p, --pretend        Run but do not make any changes
  -s, --skip           Skip files that already exist

Linking a Core Data Model

In order to keep your data model and REST webservices in sync, you can link it to your helios application:

$ helios link path/to/DataModel.xcdatamodel

This creates a hard link between the data model file in your Xcode and Helios projects—any changes made to either file will affect both. The next time you start the server, Helios will automatically migrate the database to create tables and insert columns to accomodate any new entities or attributes.

Starting the Application Locally

To run Helios in development mode on localhost, run the server command:

$ helios server

Testing Push Notifications

Once you have registered a device and set up your certificate, try this:

$ curl -X POST -d 'payload={"aps": {"alert":"Blastoff!"}}' http://localhost:5000/message

Running the Helios Console

You can start an IRB session with the runtime environment of the Helios application with the console command:

$ helios console

This command activates the services as configured by your Helios application, including any generated Core Data models. The rack module is automatically included on launch, allowing you to access everything more directly:

> Passbook::Passes.all # => [...]

Deploying to Heroku

Heroku is the easiest way to get your app up and running. For full instructions on how to get started, check out "Getting Started with Ruby on Heroku".

Once you've installed the Heroku Toolbelt, and have a Heroku account, enter the following commands from the project directory:

$ heroku create
$ git push heroku master

Integrating with an iOS Application

Core Data Synchronization

With AFIncrementalStore, you can integrate your Helios app directly into the Core Data stack. Whether it’s a fetch or save changes request, or fulfilling an attribute or relation fault, AFIncrementalStore handles all of the networking needed to read and write to and from the server.

See "Building an iOS App with AFIncrementalStore and the Core Data Buildpack" on the Heroku Dev Center for a comprehensive guide on how to use AFIncrementalStore with the Core Data buildpack. An article for Helios is forthcoming, but aside from deployment, the instructions are essentially unchanged.

Push Notification Registration

With Orbiter you can integrate Push Notifications into your app easily.

- (void)application:(UIApplication *)application
didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken
{
    NSURL *serverURL = [NSURL URLWithString:@"http://raging-notification-3556.herokuapp.com/"];
    Orbiter *orbiter = [[Orbiter alloc] initWithBaseURL:serverURL credential:nil];
    [orbiter registerDeviceToken:deviceToken withAlias:nil success:^(id responseObject) {
        NSLog(@"Registration Success: %@", responseObject);
    } failure:^(NSError *error) {
        NSLog(@"Registration Error: %@", error);
    }];
}

Converting Your Push Notification Certificate

These instructions come from the APN on Rails project.

Once you have the certificate from Apple for your application, export your key and the apple certificate as p12 files. Here is a quick walkthrough on how to do this:

  1. Click the disclosure arrow next to your certificate in Keychain Access and select the certificate and the key.
  2. Right click and choose Export 2 items….
  3. Choose the p12 format from the drop down and name it cert.p12.

Now covert the p12 file to a pem file:

$ openssl pkcs12 -in cert.p12 -out apple_push_notification.pem -nodes -clcerts

Coming Attractions

There's still a lot to do to make Helios even better. Here are some ideas that are at the top of the list:

  • Test coverage
  • More documentation
  • More example projects
  • Better RubyMotion integration
  • Support for multiple schema definitions (not just Core Data)
  • Send push notifications from the UI
  • Support for additional platforms (Android, WP7)

Contact

Mattt Thompson

License

Helios is released under the MIT license.