Observer in ruby

observer.rb

module Subject
  attr_reader :observers

  def subscribe_observer(observer)
    @observers ||= []
    @observers << observer
  end

  def unsubscribe_observer(observer)
    @observers.delete(observer)
  end

  def notify_observers(*args)
    @observers.each do |observer|
      observer.update(*args)
    end
  end
end

class WeatherData
  include Subject

  def some_action
    puts "some action take place here"
    notify_observers "some useful information "
  end
end

module Observer
  def initialize(subject)
    @subject = subject
    @subject.subscribe_observer(self)
  end

  def unsubscribe
    @subject.unsubscribe_observer(self)
  end
end

class FirstDisplay
  include Observer

  def update(info)
    puts info + "from first display"
  end
end

class SecondDisplay
  include Observer

  def update(info)
    puts info + "from second display"
  end
end

weather = WeatherData.new
first_display = FirstDisplay.new(weather)
second_display = SecondDisplay.new(weather)

weather.some_action

first_display.unsubscribe

weather.some_action