translation.rb

# This class provides most of the features you'd get from i18n-active_record,
# only simpler and lighter.
class Translation < ActiveRecord::Base
  class Backend < I18n::Backend::KeyValue
    module Implementation
      attr_reader :store

      def initialize(subtress = true)
        @store = Store.new
        super store, subtress
      end

      def available_locales
        store.locales.map &:to_sym
      end
    end

    include I18n::Backend::Memoize, Implementation
  end

  class Store
    def [](key)
      scope.find_by!(key: key).value
    rescue ActiveRecord::RecordNotFound
      nil
    end

    # FIXME: you might want to support key deletion by setting to a nil value.
    def []=(key, value)
      record = scope.find_or_initialize_by(key: key)
      record.update! value: value
    rescue ActiveRecord::RecordInvalid
      nil
    end

    def keys
      scope.pluck(:key)
    end

    # Returns a list of locales as strings using the de-normalized locale
    # column. Added to make available_locales faster.
    def locales
      scope.select(:locale).distinct.pluck(:locale)
    end

    private

    def scope
      Translation
    end
  end

  validates :locale, :key, presence: true
  validates :key, uniqueness: true

  before_validation :set_locale

  private

  # Sets a locale attribute from the key.
  def set_locale
    self.locale = locale_from key
  end

  def locale_from(key)
    $` if key =~ /\./
  end
end