Array length validator for rails

array_length_validator.rb

# app/validators/array_length_validator.rb
class ArrayLengthValidator < ActiveModel::Validations::LengthValidator
  def initialize(options)
    ActiveModel::Validations::LengthValidator::MESSAGES.each do |key, value|
      options[value] = I18n.t("errors.messages.array_#{value}")
    end
    super(options)
  end
end

en.yml

# config/locale/en.yml
en:
  errors:
    format: "%{message}"
    messages:
      array_too_long:
        one: "Do not select %{attribute}."
        other: "You can select up to %{count} %{attribute}."
      array_too_short:
        one: "Select %{attribute}."
        other: "Select at least %{count} %{attribute}."
      array_wrong_length: "Select %{count} %{attribute}."

ja.yml

# config/locale/ja.yml
ja:
  errors:
    format: "%{message}"
    messages:
      array_too_long:
        one: "%{attribute}は選択しないでください。"
        other: "%{attribute}は、最高%{count}個まで選択可能です。"
      array_too_short:
        one: "%{attribute}を選択してください。"
        other: "%{attribute}は最低%{count}個以上選択してください。"
      array_wrong_length: "%{attribute}は%{count}個選択してください。"