【Rails】I18nの言語データをDBから取得 / キャッシュ使用【i18n/i18n-active_record】

module I18n
  module Base
    def translate(*args)
      options  = args.last.is_a?(Hash) ? args.pop.dup : {}
      key      = args.shift
      backend  = config.backend
      locale   = options.delete(:locale) || config.locale
      handling = options.delete(:throw) && :throw || options.delete(:raise) && :raise # TODO: deprecate :raise
      translate_result(key, backend, locale, handling, options)
    end
    alias t translate

    def translate_result(key, backend, locale, handling, options)
      cache_key = translate_cache_key(locale, key, options)
      # キャッシュから取得orキャッシュを作成
      Rails.cache.fetch(cache_key) do
        enforce_available_locales!(locale)
        result = catch(:exception) do
          if key.is_a?(Array)
            key.map { |k| backend.translate(locale, k, options) }
          else
            backend.translate(locale, key, options)
          end
        end
        result.is_a?(MissingTranslation) ? handle_exception(handling, result, locale, key, options) : result
      end
    end

    def translate_cache_key(locale, key, options = {})
      File.join(locale.to_s, key.to_s, options.presence.to_s)
    end
  end
end

Translation.class_eval do
  after_create :create_i18n_translate_cache
  after_destroy :delete_i18n_translate_cache
  after_update :reset_i18n_translate_cache

  private

  def create_i18n_translate_cache
    I18n.t(key, locale: locale) # 一回呼んでキャッシュ作成
  end

  def delete_i18n_translate_cache
    Rails.cache.delete(delete_cache_key)
  end

  def reset_i18n_translate_cache
    delete_i18n_translate_cache
    create_i18n_translate_cache
  end

  def delete_cache_key
    I18n.translate_cache_key(locale_was, key_was)
  end
end