2017/11/22追記 Rails5からalias_method_chainは非推奨なので Module#prependを使いましょう。 メソッドをオーバーライドしたいけど元のメソッドを残したい時 ActiveSupport の alias_method_chain を使う。 class A def foo "foo" end end class B < A def foo_with_bar "foo bar" end alias_method_chain :foo, :bar end a = A.new p a.foo #=> "foo" b = B.new p b.foo #=> "foo" p b.foo_without_bar #=> "foo bar"
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