Notification system (with mailer) for Rails 4

application.rb

# SEE THE GEM https://github.com/terry90/user_notif

# config/application.rb

config.autoload_paths += %W(#{config.root}/app/models/notifications)

custom_notif.rb

# app/models/notifications/custom_notif.rb

class WelcomeNotif < Notif
  def target=(t)
    raise BadTypeNotification unless t.class == User # Create your exception in ModelException class (included in notif.rb)
    super(t)
  end

  def email_template
    'welcome_notif'
  end

  def subject_email
    I18n.t('notif.welcome.subject')
  end
end

generic_notif.html.erb

<%# app/views/notifications/mailer/generic_notif.html.erb %>

Your mail here:

Hello <%= @user.firstname %>

migration_xxxxx.rb

# db/migrate/migration_xxxxx.rb
class CreateNotifs < ActiveRecord::Migration
  def change
    create_table :notifs do |t|
      # Target is the object of the notification (like a Project, Donation or User)
      t.references :target, polymorphic: true, index: true
      t.belongs_to :user, index: true
      t.boolean :unread, index: true, default: true
      t.string :type
      t.timestamps
    end
  end
end

notif.rb

# app/models/notif.rb

# A notification must inherit from this and overload methods
class Notif < ActiveRecord::Base
  include ModelExceptions # Basic exceptions
  belongs_to :target, polymorphic: true
  belongs_to :user

  after_create :notify_email

  def email?
    true
  end

  def email_template
    'generic_notif'
  end

  def subject_email
    I18n.t('notif.generic.subject')
  end

  private

  def notify_email
    return unless email?
    NotifMailer.delay.notif_email(self.id)
  end
end

notif_mailer.rb

# app/mailers/notif_mailer.rb

class NotifMailer < ApplicationMailer
  include DefaultUrlOptions

  def notif_email(notif_id)
    notif = Notif.find(notif_id)
    @target = notif.target || raise('No target in notification mailer')
    @user = notif.user
    roadie_mail(
      to: @user.email,
      subject: notif.subject_email,
      template_path: 'notifications/mailer',
      template_name: notif.email_template
    )
  end
end

somefile.rb

def something
  # Do things
  InfosNeededNotif.create(target: @project, user: current_user)
end