decorator

decorator.rb

require 'delegate'


#----------------------------------------------------------------------
class Logger
  
  DEFAULT_FORMATTER = '%d'
  
  def initialize(formatter)
    @formatter = formatter || DEFAULT_FORMATTER
  end

  def log(*infos)
    puts @formatter % infos
  end
end


#----------------------------------------------------------------------
class MonitoredCar < SimpleDelegator
  
  def initialize(car, logger)
    super(car)
    @logger = logger
  end

  def accelerate(acc:, duration:)
    super.tap {
      @logger.log(car, speed)
    }
  end
  
  def slow_down(acc:, duration:)
    super.tap {
      @logger.log(car, speed)
    }
  end
end


#----------------------------------------------------------------------
class Car
  
  attr_reader :car, :speed

  def initialize(car)
    @car = car
    @speed = 0
  end

  def accelerate(acc:, duration:)
    delta_speed = acc * duration
    @speed += delta_speed
  end
  
  def slow_down(acc:, duration:)
    delta_speed = acc * duration
    @speed -= delta_speed
  end

end


#----------------------------------------------------------------------
def main
  car = Car.new('Ferrari')

  logger = Logger.new('-> The %s is moving at %d km/h')
  monitored_car = MonitoredCar.new(car, logger)

  monitored_car.accelerate(acc: 10, duration: 5)
  monitored_car.slow_down(acc: 10, duration: 3)
end

main()