Memento Pattern

memento.rb

class Originator
  def state=(state)
    puts "Originator: setting state to " + state
    @state = state
  end
  
  def save_to_memento
    puts "Originator: Saving to memento."
    Memento.new(@state)
  end
  
  def restore_from_memento(memento)
    state = memento.saved_state
    puts "Originator: State after restoring from Memento: " + state
  end
  
  class Memento
    attr_reader :saved_state
    def initialize(state)
      @saved_state = state
    end
  end
end

class Caretaker
  def initialize(args = [])
    saved_states = []
    originator = Originator.new
    originator.state = "State1"
    originator.state = "State2"
    saved_states << originator.save_to_memento
    originator.state = "State3"
    saved_states << originator.save_to_memento
    originator.state = "State4"
    originator.restore_from_memento(saved_states[1])
  end
end


Caretaker.new