easy_select_fields.rb

module EasySelectFields
  def easy_select_fields(a,options)
    type_method_name = "#{a}_types".to_sym
    array = options.each_with_index.map {|o,i| [o, i += 1] }

    class_eval "def self.#{a}_types() #{array.inspect} end"
  end
end

class Person
  extend EasySelectFields
  easy_select_fields "status", ["Interested", "Not Interested", "Available"]
end

non_inspectable.rb

require "active_support/core_ext/kernel/singleton_class"

module EasySelectFields
  def easy_select_fields(a,options)
    type_method_name = "#{a}_types".to_sym
    array = options.each_with_index.map {|o,i| [o, i] }

    singleton_class.class_eval do
      define_method("#{a}_types") { array }
    end
  end
end

class Person
  extend EasySelectFields
  easy_select_fields "status", ["Interested", "Not Interested", "Available"]
end