Abstract Notifier

Abstract Notifier is a tool which allows you to describe/model any text-based notifications (such as Push Notifications) the same way Action Mailer does for email notifications.

Abstract Notifier (as the name states) doesn't provide any specific implementation for sending notifications. Instead, it offers tools to organize your notification-specific code and make it easily testable.

📖 Read the introduction post: "Crafting user notifications in Rails with Active Delivery"

Requirements:

• Ruby ~> 2.4

NOTE: although most of the examples in this readme are Rails-specific, this gem could be used without Rails/ActiveSupport.

Installation

Add this line to your application's Gemfile:

gem "abstract_notifier"

And then execute:

$ bundle

Usage

Notifier class is very similar to Action Mailer mailer class with notification method instead of a mail method:

class EventsNotifier < ApplicationNotifier
  def canceled(profile, event)
    notification(
      # the only required option is `body`
      body: "Event #{event.title} has been canceled",
      # all other options are passed to delivery driver
      identity: profile.notification_service_id
    )
  end
end

# send notification later
EventsNotifier.canceled(profile, event).notify_later

# or immediately
EventsNotifier.canceled(profile, event).notify_now

To perform actual deliveries you must configure a delivery driver:

class ApplicationNotifier < AbstractNotifier::Base
  self.driver = MyFancySender.new
end

A driver could be any callable Ruby object (i.e., anything that responds to #call).

That's a developer responsibility to implement the driver (we do not provide any drivers out-of-the-box; at least yet).

You can set different drivers for different notifiers.

Parameterized notifiers

Abstract Notifier support parameterization the same way as Action Mailer:

class EventsNotifier < ApplicationNotifier
  def canceled(event)
    notification(
      body: "Event #{event.title} has been canceled",
      identity: params[:profile].notification_service_id
    )
  end
end

EventsNotifier.with(profile: profile).canceled(event).notify_later

Defaults

You can specify default notification fields at a class level:

class EventsNotifier < ApplicationNotifier
  # `category` field will be added to the notification
  # if missing
  default category: "EVENTS"

  # ...
end

NOTE: when subclassing notifiers, default parameters are merged.

You can also specify a block or a method name as the default params generator. This could be useful in combination with the #notification_name method to generate dynamic payloads:

class ApplicationNotifier < AbstractNotifier::Base
  default :build_defaults_from_locale

  private

  def build_defaults_from_locale
    {
      subject: I18n.t(notification_name, scope: [:notifiers, self.class.name.underscore])
    }
  end
end

Background jobs / async notifications

To use notify_later you must configure async_adapter.

We provide Active Job adapter out-of-the-box and use it if Active Job is present.

The custom async adapter must implement enqueue method:

class MyAsyncAdapter
  # adapters may accept options
  def initialize(options = {})
  end

  # `enqueue` method accepts notifier class and notification
  # payload.
  # We need to know notifier class to use its driver.
  def enqueue(notifier_class, payload)
    # your implementation here
  end
end

# Configure globally
AbstractNotifier.async_adapter = MyAsyncAdapter.new

# or per-notifier
class EventsNotifier < AbstractNotifier::Base
  self.async_adapter = MyAsyncAdapter.new
end

Delivery modes

For test/development purposes there are two special global delivery modes:

# Track all sent notifications without peforming real actions.
# Required for using RSpec matchers.
#
# config/environments/test.rb
AbstractNotifier.delivery_mode = :test

# If you don't want to trigger notifications in development,
# you can make Abstract Notifier no-op.
#
# config/environments/development.rb
AbstractNotifier.delivery_mode = :noop

# Default delivery mode is "normal"
AbstractNotifier.delivery_mode = :normal

NOTE: we set delivery_mode = :test if RAILS_ENV or RACK_ENV env variable is equal to "test". Otherwise add require "abstract_notifier/testing" to your spec_helper.rb / rails_helper.rb manually.

NOTE: delivery mode affects all drivers.

Testing

Abstract Notifier provides two convinient RSpec matchers:

# for testing sync notifications (sent with `notify_now`)
expect { EventsNotifier.with(profile: profile).canceled(event).notify_now }
  .to have_sent_notification(identify: "123", body: "Alarma!")

# for testing async notifications (sent with `notify_later`)
expect { EventsNotifier.with(profile: profile).canceled(event).notify_later }
  .to have_enqueued_notification(identify: "123", body: "Alarma!")

NOTE: test mode activated automatically if RAILS_ENV or RACK_ENV env variable is equal to "test". Otherwise add require "abstract_notifier/testing/rspec" to your spec_helper.rb / rails_helper.rb manually. This is also required if you're using Spring in test environment (e.g. with help of spring-commands-rspec).

Related projects

active_delivery

Active Delivery is the next-level abstraction which allows combining multiple notification channels in one place.

Abstract Notifier provides a notifier line for Active Delivery:

class ApplicationDelivery < ActiveDelivery::Base
  # Add notifier line to you delivery
  register_line :notifier, ActiveDelivery::Lines::Notifier,
                # you may provide a resolver, which infers notifier class
                # from delivery name (resolver is a callable).
    resolver: ->(name) { resolve_somehow(name) }
end

NOTE: we automatically add :notifier line with "*Delivery" -> *Notifier resolution mechanism if #safe_constantize method is defined for String, i.e., you don't have to configure the default notifier line when running Rails.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/palkan/abstract_notifier.

License

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