Dropdown list validation on rails > 3.2

gistfile1.rb

  class Person
    validates :gender_id,     :presence => true, :inclusion => { :in => proc { |req| req.gender_types.map{ |key, value| key } } } #req - self 'Person' object
    validates :title_id,      :presence => true, :inclusion => { :in => proc { |req| req.title_types.map{ |key, value| key } } }
  end