ruby オブジェクト設計

単一責任

変更に対応できるように

- wheelの切り出し

単一責任の為に

- initailizeの while=nil

変動に対応する

class Gear 
  attr_reader :chainring, :cog, :wheel

  def initialize(chainring, cog, wheel=nil)
    @chainring = chainring
    @cog = cog 
    @wheel = wheel
  end

  def ratio
    chainring / cog.to_f
  end

  def gear_inches
    ratio * wheel.diameter
  end
end

class Wheel
  attr_reader :rim, :tire

  def initialize(rim, tire)
    @rim = rim
    @tire = tire
  end

  def diameter
    rim + (tire * 2)
  end

  def circumference
    diameter * Math::PI
  end
end

@wheel = Wheel.new(26, 1.5)

p @wheel.circumference

gear2 = Gear.new(11,11,@wheel)


p gear2.gear_inches

　引数のコントロール

• ハッシュで格納

arges = ハッシュ

• 引数の格納順番への依存はなくなる

class Gear

  attr_reader :chinring, :cog, :wheel

  def initialize(arges)
    @chinring = arges[:chinring]
    @cog = arges[:cog]
    @wheel = arges[:wheel]
  end

  def fog
    chinring + cog + wheel
  end
end

class Wheel
  attr_reader :ring

  def initialize(ring)
    @ring = ring
  end

  def ee
   ring
  end

end

p Gear.new(chinring: 52, cog: 11, wheel: Wheel.new(11).ee ).fog