Rails模型中的復合場

Question

我在Rails中有這個模型：

class PaymentsDcument < ActiveRecord::Base
  attr_accessible :date, :domain, :id,  :total, :paid, :paid_left, :percentage
end

並且我想添加字段payment_total = total*percentage而無需在數據庫中創建該字段。

Answer 1

有些人將Presenter用於此類代碼，但是您可以選擇

class PaymentsDcument < ActiveRecord::Base
  attr_accessible :date, :domain, :id,  :total, :paid, :paid_left, :percentage

  def payment_total
    total*percentage
  end
end