Mémento en Ruby

# The Originator holds some important state that may change over time. It also # defines a method for saving the state inside a memento and another method for # restoring the state from it. class Originator # For the sake of simplicity, the originator's state is stored inside a single # variable. attr_accessor :state private :state # @param [String] state def initialize(state) @state = state puts "Originator: My initial state is: #{@state}" end # The Originator's business logic may affect its internal state. Therefore, # the client should backup the state before launching methods of the business # logic via the save() method. def do_something puts 'Originator: I\'m doing something important.' @state = generate_random_string(30) puts "Originator: and my state has changed to: #{@state}" end private def generate_random_string(length = 10) ascii_letters = [*'a'..'z', *'A'..'Z'] (0...length).map { ascii_letters.sample }.join end # Saves the current state inside a memento. def save ConcreteMemento.new(@state) end # Restores the Originator's state from a memento object. def restore(memento) @state = memento.state puts "Originator: My state has changed to: #{@state}" end end # The Memento interface provides a way to retrieve the memento's metadata, such # as creation date or name. However, it doesn't expose the Originator's state. class Memento # @abstract # # @return [String] def name raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'" end # @abstract # # @return [String] def date raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'" end end class ConcreteMemento < Memento # @param [String] state def initialize(state) @state = state @date = Time.now.strftime('%F %T') end # The Originator uses this method when restoring its state. attr_reader :state # The rest of the methods are used by the Caretaker to display metadata. def name "#{@date} / (#{@state[0, 9]}...)" end # @return [String] attr_reader :date end # The Caretaker doesn't depend on the Concrete Memento class. Therefore, it # doesn't have access to the originator's state, stored inside the memento. It # works with all mementos via the base Memento interface. class Caretaker # @param [Originator] originator def initialize(originator) @mementos = [] @originator = originator end def backup puts "\nCaretaker: Saving Originator's state..." @mementos << @originator.save end def undo return if @mementos.empty? memento = @mementos.pop puts "Caretaker: Restoring state to: #{memento.name}" begin @originator.restore(memento) rescue StandardError undo end end def show_history puts 'Caretaker: Here\'s the list of mementos:' @mementos.each { |memento| puts memento.name } end end originator = Originator.new('Super-duper-super-puper-super.') caretaker = Caretaker.new(originator) caretaker.backup originator.do_something caretaker.backup originator.do_something caretaker.backup originator.do_something puts "\n" caretaker.show_history puts "\nClient: Now, let's rollback!\n" caretaker.undo puts "\nClient: Once more!\n" caretaker.undo 

Originator: My initial state is: Super-duper-super-puper-super. Caretaker: Saving Originator's state... Originator: I'm doing something important. Originator: and my state has changed to: CHYzYSIWbqvWkCzIHOqTyEJWfQlFMn Caretaker: Saving Originator's state... Originator: I'm doing something important. Originator: and my state has changed to: vbkhwCeAEQBpLwQLlhmpcvUnwzxVnT Caretaker: Saving Originator's state... Originator: I'm doing something important. Originator: and my state has changed to: SBWlQnAEPLsitiOQAZbGlXHZAeWBoW Caretaker: Here's the list of mementos: 2023-08-11 15:02:35 / (Super-dup...) 2023-08-11 15:02:35 / (CHYzYSIWb...) 2023-08-11 15:02:35 / (vbkhwCeAE...) Client: Now, let's rollback! Caretaker: Restoring state to: 2023-08-11 15:02:35 / (vbkhwCeAE...) Originator: My state has changed to: vbkhwCeAEQBpLwQLlhmpcvUnwzxVnT Client: Once more! Caretaker: Restoring state to: 2023-08-11 15:02:35 / (CHYzYSIWb...) Originator: My state has changed to: CHYzYSIWbqvWkCzIHOqTyEJWfQlFMn