RC 1もリリースされて流石にもう増える事はないと思うので、Rails 5で追加されたinitializerについてざっとまとめてみる。 # config/initializers/active_record_belongs_to_required_by_default.rb # Require `belongs_to` associations by default. This is a new Rails 5.0 # default, so it is introduced as a configuration option to ensure that apps # made on earlier versions of Rails are not affected when upgrading. Rails.application.config.active_record.belo