Rails模型中的复合场

Question

I have this model in Rails:

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

and I want to add the field payment_total = total*percentage without creating the field in the database.

Answer 1

Some people use a Presenter for this kind of code, but you could go with

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

  def payment_total
    total*percentage
  end
end