virtual_date.rb

module VirtualDate
  extend ActiveSupport::Concern

  class_methods do
    def virtual_date(name)
      attr_reader name

      # Incoming forms pass dates as a hash like {1 => 2014, 2 => 4, 3 => 30}
      # This converts that to a date class instance
      define_method("#{name}=") do |new_value|
        if new_value.is_a?(Hash)
          new_value = Date.new(*(new_value.sort.map(&:last)))
        end
        self.instance_variable_set("@#{name}", new_value)
      end
    end
  end
end