custom_dirty_tracking

🔥 Customize Dirty Tracking for Virtual Attributes

Sometimes you want to treat virtual attributes (not persisted in the DB) as part of the dirty tracking API. Override attribute_will_change! and attribute_changed? to hook into ActiveModel’s dirty tracking for in‑memory attributes.

class Invoice < ApplicationRecord
  attr_accessor :discount_code

  def discount_code=(val)
    discount_code_will_change! unless val == @discount_code
    @discount_code = val
  end

  def discount_code_changed?
    attribute_changed?(:discount_code)
  end
end

Now you get invoice.discount_code_changed?, invoice.changes, and invoice.save won’t persist it but will show you changed state for downstream logic.