PushToSNS

PushToSNS is an opinionated gem to allow pushing push notifications through SNS. It assumes you want to use a type and a message in your payload, that you already configured the AWS gem and that your message is encoded as json. If this is your case, this will make your life easier.

Add this line to your application's Gemfile:

gem "push_to_sns"

And then execute:

$ bundle

1. First, configure the AWS gem.

2. Now, run the following command if you use rails:

   $ rails generate push_to_sns:install
   

This will generate the file app/initializers/push_to_sns.rb with the following content: (if you're not using rails, just paste the code in a place to be executed once on startup)

  PushToSNS.configure do
    read_device_token { |device| }
    read_source { |device| }
    read_endpoint_arn { |device| }
    read_platform_arn { |device|  }
    read_ios_apns { |device| }

    save_endpoint_arn do |device, endpoint_arn|
    end
  end

3. This initializer is only full of some empty methods. Why? Because we don't want to enforce a Device model or couple heavily with ActiveRecord, you can specify the way you want us to read and store device identifiers and SNS endpoints in your model. We don't want to be an obstacle in your way. But, anyway, we can suggest the following:

  PushToSNS.configure do
    read_device_token { |device| device.device_token }
    read_source { |device| device.source }
    read_endpoint_arn { |device| device.endpoint_arn }
    read_platform_arn { |device| ENV["SNS_#{device.source.upcase}_PLATFORM_ARN"] }
    read_ios_apns { ENV["APNS"] }

    save_endpoint_arn do |device, endpoint_arn|
      device.update(endpoint_arn: endpoint_arn)
    end
  end

This is up to you in some way. For example, you can have a controller to receive a device_token and device_uuid from a mobile device and you want to register the device to be able to receive push notifications. You can do it in this way:

class DevicesController < ApiController
  def create
    device = Device.find_by(device_uuid: device_params[:device_uuid])
    if device.present?
      # We first teardown the old endpoint arn.
      PushToSNS.teardown_device(device)
      device.update(device_params.slice(:device_token))
    else
      device = Device.create(device_params)
    end

    PushToSNS.setup_device(device)
    respond_with device
  end

  private

  def device_params
    params.require(:device).permit(:device_token, :device_uuid, :source)
  end
end

PushToSNS.setup_device will get the device identifier from the object passed and register it on SNS. Then, it will store the endpoint returned using the code specified in save_endpoint_arn configuration.

Now, imagine you have a football match and you want to notify users about a new goal being made. First, create a push notification object. In Rails, you can do this:

rails generate push_to_sns:notifier new_goal goal

The parameter new_goal will be used to set the notifier's name and the next parameters (goal, for example) will be used to add some attribute accessors to the new notifier. This will help with the initialization of the notifier.

It will create the following object in app/push_notifiers/new_goal_push_notifier.rb:

class NewGoalPushNotifier < PushToSNS::PushNotifier
  message "New Goal"
  type :new_goal

  attr_accessor :goal

  def devices
    fail "Method Not Implemented: devices"
  end

  def notification(device)
    fail "Method Not Implemented: notification"
  end
end

Now, we need to answer two questions:

• What devices do we need to notify of this goal?
• What is the data we need to send?

To answer these questions, we need to implement the method devices and notification. For example, we can have these two methods:

def devices
  goal.match.subscribed_devices
end

def notification(device)
  {
    scorer: goal.scorer,
    team: goal.team,
    match_id: goal.match_id,
    new_result: goal.new_result,
    is_favorite: device.user.favorite_teams.include?(goal.team)
  }
end

Now, in whatever place you want to, deliver the notifier by creating a push notifier with the given arguments (those attribute accesors that we set before) and calling deliver after that:

NewGoalPushNotifier.new(goal: goal).deliver

After checking out the repo, run bin/setup to install dependencies. Then, run rake false to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/push_to_sns.

The gem is available as open source under the terms of the MIT License.