如何在 Rails 中“验证"销毁

问题描述

在销毁一个安静的资源时，我想在允许销毁操作继续之前保证一些事情?基本上，如果我注意到这样做会使数据库处于无效状态，我希望能够停止销毁操作?销毁操作没有验证回调，那么如何验证"销毁操作是否应该被接受?

On destruction of a restful resource, I want to guarantee a few things before I allow a destroy operation to continue? Basically, I want the ability to stop the destroy operation if I note that doing so would place the database in a invalid state? There are no validation callbacks on a destroy operation, so how does one "validate" whether a destroy operation should be accepted?

推荐答案

您可以引发一个异常，然后捕获该异常.Rails 将删除包含在事务中，这有助于解决问题.

You can raise an exception which you then catch. Rails wraps deletes in a transaction, which helps matters.

例如:

class Booking < ActiveRecord::Base
  has_many   :booking_payments
  ....
  def destroy
    raise "Cannot delete booking with payments" unless booking_payments.count == 0
    # ... ok, go ahead and destroy
    super
  end
end

或者，您可以使用 before_destroy 回调.此回调通常用于销毁依赖记录，但您可以抛出异常或添加错误.

Alternatively you can use the before_destroy callback. This callback is normally used to destroy dependent records, but you can throw an exception or add an error instead.

def before_destroy
  return true if booking_payments.count == 0
  errors.add :base, "Cannot delete booking with payments"
  # or errors.add_to_base in Rails 2
  false
  # Rails 5
  throw(:abort)
end

myBooking.destroy 现在将返回 false，并且 myBooking.errors 将在返回时填充.

myBooking.destroy will now return false, and myBooking.errors will be populated on return.

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