ruby_classes_evented.rb

require 'singleton'

class Subscriber
  include Singleton
  attr_reader :subscriptions

  def initialize
    @subscriptions = {}
  end

  def subscribe(event_name, callback)
    subscriptions[event_name] = (subscriptions[event_name] || []).push(callback)
  end
end

class Base
  def self.run
    new.run
  end

  def self.subscribe(event)
    subscriber.subscribe(event, self)
  end

  def self.subscriber
    Subscriber.instance
  end

  def emit(event, _data = nil)
    Base.subscriber.subscriptions[event].each(&:run)
  end
end

class B < Base
  def run
    puts "B subscribed to event"
  end
end

class C < Base
  def run
    puts "C subscribed to event"
  end
end

class A < Base
  def run
    while true
      emit(:periodic_event)
      sleep 5
    end
  end
end

B.subscribe(:periodic_event)
C.subscribe(:periodic_event)
A.run