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Ruby の module のインスタンス...

Last updated at Posted at 2021-12-13

はじめに

移植やってます
Python to Ruby Advent Calendar 2021

インスタンス変数

module A
  Al = 0
  @Ai = 0
  @@Aa = 0
end

class B
  include A

  Bl = 0
  @Bi = 0
  @@Bc = 0
end
p ['instance_variables: ', A.instance_variables, B.instance_variables]
p ['class_variables: ', A.class_variables, B.class_variables]

# ["instance_variables: ", [:@Ai], [:@Bi]]
# ["class_variables: ", [:@@Aa], [:@@Bc, :@@Aa]]

モジュールはインスタンス化できないけど、インスタンス変数はあるってことですね。
モジュールのクラス変数が、上記class Bにも表れているのが不思議。

[追記]
コメント欄に、ありがたい情報があります。
@scivola さん、ありがとうございます。

module A
  @Ai = 0
  @@Ac = 0

  def seti(value)
    @Ai = value
  end

  def setc(value)
    @@Ac = value
  end

  def geti
    @Ai
  end

  def getc
    @@Ac
  end
end

class B
  include A

  def seti(value)
    super
  end

  def setc(value)
    super
  end

  def geti
    super
  end

  def getc
    super
  end
end

class C
  include A

  def seti(value)
    super
  end

  def setc(value)
    super
  end

  def geti
    super
  end

  def getc
    super
  end
end


b = B.new
c = C.new
b.seti(2)
b.setc(5)
p [b.geti, b.getc, c.geti, c.getc]

# [2, 5, nil, 5]

module class B/C のインスタンス変数ですので別になっています。

メモ

  • Ruby の module を学習した
  • 道のりは遠そう
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