Apple Push Notification Service in Rails

Push Notifications Overview

Getting push to work for your app takes quite a bit of effort. This is a puzzle with many pieces. Here is an overview:

1. An app enables push notifications. The user has to confirm that he wishes to receive these notifications.
2. The app receives a “device token”. You can think of the device token as the address that push notifications will be sent to.
3. The app sends the device token to your server.
4. When something of interest to your app happens, the server sends a push notification to the Apple Push Notification Service, or APNS for short.
5. APNS sends the push notification to the user’s device.

Converting and Adding Certificate

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 convert the p12 file to a pem file:

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

If you are using a development certificate, then change the name to apple_push_notification_development.pem instead. Add the .pem file in config/ directory of the Rails application.

Installing Gem for Push Notifications

Gem to use for Apple push notifications is “apn_on_rails” Github Link
To add the gem to your Rails app just add this line to your Gemfile.

'gem apn_on_rails'

or Type in this command at terminal

$ sudo gem install apn_on_rails

Registering your App for Apple Push Notifications

Before adding push notification service to your Rails app, you have to register your app for the Push Notification Service with the certificate created earlier.

Register your App with credentials as (Ruby Code)

app = APN::App.new
app.apn_dev_cert = File.read('config/apple_push_notification_development.pem')
app.save

The code creates a new APN::App, adds a Developer certificate and saves it to the database.

Registering the devices of the users to your Rails Application

After registering the app for push notifications, The next step is to register the devices of all the users of your Application. Registering the user devices to the service is through there “device tokens”. When the user registers to the app in the “client side”, the device token is retrieved and sent to the “Rails App” in the POST request.
Use that device tokens to register the users for the Apple Push Notification Service.

Register the users to the service as (Ruby code)

device = APN::Device.new
device.token = self.device_token
device.app_id=app.id
device.save

The code creates a new App Device Instance. Adds the device token of the user fetched from the client app. Adds an app_id to the device with the id of your App created earlier and then save the device to the database. Now your user is ready to accept the Push Notification from the server.

Single Notifications

If you want to send individual notifications.

notification = APN::Notification.new
notification.device = device
notification.badge = 5
notification.sound = true
notification.alert = "Message by Admin"
notification.save

The code creates a Notification Instance. Adds a device you want to send notifications too. Adds badge, sound and alert message to the notification and save it to the database.
Then the send the notification to the device using

 APN::App.send_notifications

Group Notifications

The gem does has support for group notificatiosn too. Sending messages to many devices at the same time.

Get all the registered devices using

devices = APN::Device.all

Get the App registered for the service

app = APN::App.first

For sending group notifications,we have to create a group and add the devices array to the group.

Create a group and add name and app_id and save it to the database

  group = APN::Group.new
  group.name = 'products'
  group.app_id = app.id
  group.save

Adding the devices array to the group

group.devices = devices

Adding a Group Notification

Create a Group Notification instance. Add the group instance to the notification group. Add alert, badge messages and save it to the database

notification = APN::GroupNotification.new
notification.group = group
notification.alert = 'Event got locked'
notification.badge = 4
notification.sound = true
notification.save

Then send the Group notification to all the devices as

 APN::App.send_group_notifications
APN::App.process_devices

This sends the message to all the devices registered.