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http://jewelrybox.wpblog.jp/2017/10/25/ruby-rails%e3%83%aa%e3%83%95%e3%82%a1%e3%83%ac%e3%83%b3%e3%82%b9%e3%82%b5%e3%82%a4%e3%83%88%e3%80%8crails-guides%e3%80%8d/
Ruby on Railsリファレンスサイト「RAILS GUIDES」