Events

events.rb

require 'bundler/setup'
Bundler.require :default

require 'securerandom'
require 'active_support/notifications'
require 'active_support/concern'

module Events
  include ActiveSupport::Concern

  def on(event_type, &handler)
    ActiveSupport::Notifications.subscribe(event_type) do |*args|
      event = ActiveSupport::Notifications::Event.new(*args)
      handler.call(event)
    end
  end

  def fire(event_type)
    ActiveSupport::Notifications.instrument(event_type, target: self)
  end

  module ClassMethods
    def on(object, event_type, &handler)
      ActiveSupport::Notifications.subscribe(event_type, &handler)
    end

    def fire(object, event_type)
      ActiveSupport::Notifications.instrument(event_type, target: object)
    end
  end
end

bob = Object.new
bob.extend Events
bob.on 'message' do |event|
  data = {name: event.name, duration: event.duration, payload: event.payload}
  puts "bob got: #{data.inspect}"
end

bob.fire 'message'
bob.fire 'nohandler'
bob.fire 'message'