Ruby - Initializing Instances: Off to a Great Start(Using optional parameters with "initialize")

Head First Ruby

開発環境

• OS X El Capitan - Apple (OS)
• Emacs (Text Editor)
• Ruby 2.3 (プログラミング言語)

Head First Ruby (Jay McGavren (著)、O'Reilly Media)のChapter 4.(Initializing Instances: Off to a Great Start)、Using optional parameters with "initialize"、POOL PUZZLE(No. 2412)を取り組んでみる。

POOL PUZZLE(No. 2412)

コード(Emacs)

#!/usr/bin/env ruby2.3
# -*- coding: utf-8 -*-

class Car
  def initialize(engine)
    @engine = engine
  end
  def rev_engine
    @engine.make_sound
  end
end

class Engine
  def initialize(sound = "Vroom!!")
    @sound = sound
  end
  def make_sound
    puts @sound
  end
end

engine = Engine.new
car = Car.new(engine)
car.rev_engine

入出力結果(Terminal)

$ ./pool_puzzle.rb
Vroom!!
$