class Car
  attr_reader :steering_wheel
 
  def initialize(steering_wheel)
    @steering_wheel = steering_wheel
  end
 
  def start_engine
    # do something
  end
end
 
class SteeringWheel
  def turn_left
    # turn the car to the left
  end
 
  def turn_right
    # turn the car to the right
  end
end
 
a_car = Car.new(SteeringWheel.new)
a_car.start_engine
a_car.steering_wheel.turn_left
a_car.steering_wheel.turn_right