#---
# Excerpted from "Programming Ruby 3.2",
# published by The Pragmatic Bookshelf.
# Copyrights apply to this code. It may not be used to create training material,
# courses, books, articles, and the like. Contact us if you are in doubt.
# We make no guarantees that this code is fit for any purpose.
# Visit https://pragprog.com/titles/ruby6 for more book information.
#---
module Observable
  def observers
    @observer_list ||= []
  end

  def add_observer(obj)
    observers << obj
  end

  def notify_observers
    observers.each { |o| o.update }
  end
end
