RoR：同一模型中的has_one和has_many引用？

Question

Say I have a model called Device, and another model called Firmware (which contains a firmware version number and other info). I would like to keep track of the history of firmware versions installed on the device, but also a reference to the current version (which may or may not be the most recent date-wise).

How do I set up my associations so that I can point to one specific firmware configuration (the current one) and also several different firmware configurations (the history)?

Answer 1

Add device_current_id integer column to the firmwares table and then:

class Device < ActiveRecord::Base
  ...
  has_one :current_firmware, class_name: "Firmware", foreign_key: "device_current_id"
  has_many :firmwares
end

Answer 2

Use :class_name in you associations like...

Device Model

has_one :current_firmware, class_name :firmware
has_many :old_firmwares, class_name :firmware