Display proper Korean particles in error messages

korean_error_messages.rb

# encoding: UTF-8
    # Original article: http://dailyupgrade.me/post/6806676778/rubyonrails-full-messages-for-korean
    # Modified to support more postpositions and client_side_validations gem.
    #
    # Add Korean translations like this:
    #   ko:
    #     errors:
    #       format: "%{message}"
    #       messages:
    #         blank: "%{attribute}((이)) 입력되지 않았습니다"
    #         taken: "이미 사용 중인 %{attribute}입니다"
    #         invalid: "잘못된 %{attribute}입니다"
    #         too_short: "%{attribute}((이)) 너무 짧습니다"
    #

    class Korean

      POSTPOSITIONS = {"은" => "는", "이" => "가", "을" => "를", "과" => "와", "으로" => "로"}

      def self.select_postposition(last_letter, postposition)
        return postposition unless last_letter >= "가" && last_letter <= "힣"
        final = last_letter.mb_chars.last.decompose[2]
        if final.nil?
          # 받침 없음
          POSTPOSITIONS[postposition] || postposition
        elsif final == "ㄹ" && (postposition == "으로" || postposition == "로")
          # 'ㄹ 받침 + (으)로'를 위한 특별 규칙
          "로"
        else
          # 받침 있음
          POSTPOSITIONS.invert[postposition] || postposition
        end
      end
    end

    module ActiveModel

      class Errors

        old_generate_message = instance_method("generate_message")

        define_method("generate_message") do |attribute, type = :invalid, options = {}|
          msg = old_generate_message.bind(self).(attribute, type, options)
          return msg unless I18n.locale == :ko
          msg.gsub(/(?<=(.{1}))\(\((은|는|이|가|을|를|과|와|으로|로)\)\)/) do
            Korean.select_postposition $1, $2
          end
        end
      end
    end