module Observable2
  def add_observer observer
    @observable_observers ||= []
    @observable_observers << observer unless @observable_observers.include? observer      
  end
  
  def notify_observers method, *args
    raise "Invalid usage, method must be Symbol or String!" unless method.is_a?(Symbol) or method.is_a?(String)
    @observable_observers.each{|observer| observer.respond_to method, *args} if @observable_observers      
  end
  
  def delete_observer observer
    @observable_observers.delete observer if @observable_observers
  end
  
  def delete_observers      
    @observable_observers.clear if @observable_observers
  end
  
  def observers_count
    @observable_observers ? @observable_observers.size : 0
  end
end