gem 'chilean_rut'

class RUTValidator < ActiveModel::Validator
  require 'chilean_rut'
  def validate(record)
    unless RUT::validate(record.rut)
      record.errors[:rut] << I18n.t(:invalid_rut)
    end
  end
end

class Person < ActiveRecord::Base
  validates_with RUTValidator
end

require 'chilean_rut'

rut = '55.555.555-5'
puts RUT::validate(rut) ? 'VALIDO' : 'NO VALIDO' # VALIDO
puts RUT::format(rut) # 55.555.555-5
puts RUT::remove_format(rut) # 555555555
puts RUT::remove_points(rut) # 55555555-5
puts RUT::remove_hyphens(rut) # 55.555.5555