在ActiveRecord模型中定义临时属性

Question

我想在ActiveRecord模型中保存临时属性。

class Order < ActiveRecord::Base
  attr_accessor :order_total

  def order_total
    self[:order_total] = self.sale_sum + self.freight_charges
  end
end

order = Order.find(1)
order.order_total

我的问题是：如何在ActiveRecord模型中定义虚拟（又名临时）属性？

Answer 1

class Order < ActiveRecord::Base

  def order_total
    sale_sum + freight_charges
  end

end

order = Order.find(1)
order.order_total # will eq to sale_sum + freight_charges