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Ruby のオープンクラスとは (メタプログラミングRuby)

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Rubyでは定義済みのクラスでも、何度でも開いて、中身をいじることが出来る。
これをオープンクラスという。

クラスを定義

クラスメソッドを1個作る。

class A
  def some_method
    p :some_method
  end
end

また定義

メソッドをもう1個作る。

class A
  def new_method
    p :new_method
  end
end

すると‥

どちらのメソッドも呼べるようになる

A.new.some_method # :some_method
A.new.new_method # :new_method

なんでもアリ

Integer クラスなど、元から存在するクラスでもオープンして書き換えられる。

class Integer
  def some_method
    p :some_method
  end
end

1.some_method # :some_method
2.some_method # :some_method

参考

  • メタプログラミングRuby
YumaInaura
Ruby on Rails 業務経験 約5年 / Perl PHP Python Golang Linux Apache MySQL BigQuery Jenkins ansible AWS など / いなうらゆうま / YumaInaura / 稲浦悠馬
http://twitter.com/yumainaura
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