rails 3 validation outside model (active record)

validation-outside.rb

########

class ActivationCode
    include ActiveModel::Validations
    
    attr_accessor :activation_code
    validates :activation_code, :presence => true

    def initialize(activation_code)
      @activation_code = activation_code
    end
end

########
class CheckController < ApplicationController
  def activation
    u = ActivationCode.new :activation_code => params[:code]
    u.valid?
  end
end