ActiveRecord モデルの validates をコピー

application_form.rb

 class ApplicationForm
  include ActiveModel::Model
  include ActiveModel::Attributes

  def self.copy_validations_from(model)
    attribute_types.keys.each do |key|
      model.validators_on(key).each do |validator|
        validates(key, validator.kind => validator.options)
      end
    end
  end
end