User Notifier

User Notifier creates a very simple pattern to store and manage event generated notifications for the users of a Rails application It's an engine that will create Model and Mailer objects on the fly as well as a Sidekiq worker to send email in the background. Although the gem was developed assuming that these notifications are all delivered by email, it would not be difficult to extend it for other kinds of message.

Installation

Include in your Gemfile:

gem 'user_notifier'

Then run:

rails g user_notifier:install

This will create an initializer in config/initializers/user_notifier.rb Take a look in this initializer to tweak the default attributes of notifications.

Notification sources and recipient

This gem assumes that all notifications can be represented as a relation mapping a source (some model tied to the event that triggered the notification) to a recipient (a user of your application).

Generating a notification recipient

As we assume that all recipients are users in your system, we just need to tell the engine which model stores these users. This can be done in the initializer generated during the installation. Assuming you have a model called User the default initializer will work for you:

UserNotifier.configure do |config|
  config.user_class_name  = 'User'
end

Generating a notification source

Let's assume that our system have a model called Order. This model generates notifications for users in several different occasions. But all these events share the same model as a common source for the notification, so we consider Order to be our notification source. Therefore we should create a database table to store all these notifications. We use the notification generator:

rails g user_notifier:notification order
rake db:migrate

Now that this migration created a table to store our notifications from that source we can add the code in the model that includes the notify methods:

class Order < ActiveRecord::Base
  has_notifications
end

That's all, now we have the Order model as a notification source and events in this model can send notifications to users in the User model. All this notifications can me accessed in the notifications associations like in Order.first.notifications

Creating templates for the notifications

All notifications templates should be stored in user_notifier/mailer/ in your views directory. You should create at least two views for each notification you want to send, one for the body of the email and another one for the subject. Let's say we want to create a notification to users when orders are confirmed. We can call this the order_confirmed notification and create two templates:

user/notifier/mailer/order_confirmed.html.erb
user/notifier/mailer/order_confirmed_subject.html.erb

Inside the templates we can use the @notification to access notification attributes. The @notification.source or @notification.order will give access to the order model linked to the notification. The @notification.user will give access to the user model (this association name can vary according to the configuration but user is the default).

Sending notifications

Now to send an order_confirmed notification we simply call the method notify as in:

user = User.first
order = Order.first
order.notify(:order_confirmed, user)

This project rocks and uses MIT-LICENSE.