给类对象添加一个随机生成序号

module SerialNumber
  def self.included(base)
     base.extend(ClassMethods)
  end
 module ClassMethods
  def create_sn
    year_code=%w{A B C D E F G H I J K}
    month_code=%w{1 2 3 4 5 6 7 8 9 A B C D E F}
    day_code=%w{1 2 3 4 5 6 7 8 9 A B C D E F G H I J K L M N O P Q R S T U V W}
    year_sn = year_code[Time.now.year-2014] # 1 bit
    month_sn = month_code[Time.now.month-1] # 1 bit
    day_sn = day_code[Time.now.day] # 1 bits
    sec_sn = (Time.now.to_i.to_s)[-5..-1] # 5 bits
    millisecond_sn = Time.now.strftime("%3N").to_s # 3 bits
    #microsecond_sn = Time.now.strftime("%6N").to_s # 6 bits
    rand_sn = rand(99).to_s.rjust(2,"0") #2 bits
    year_sn+month_sn+day_sn+sec_sn+millisecond_sn+rand_sn # 13 bits
  end
 end
end



class Order < Base
  include SerialNumber
end


order = Order.new
order.code = order.class.create_sn
order.save