在销毁一个宁静的资源时，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”是否应该接受销毁操作？
Samedhi
问问题
57423 次
11 回答
74
您可以引发一个异常，然后捕获该异常。Rails 将删除包装在事务中，这有助于解决问题。
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。
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，并将myBooking.errors在返回时填充。
于 2008-09-23T19:22:37.723 回答
49
只是一个说明：
用于导轨 3
class Booking < ActiveRecord::Base
before_destroy :booking_with_payments?
private
def booking_with_payments?
errors.add(:base, "Cannot delete booking with payments") unless booking_payments.count == 0
errors.blank? #return false, to not destroy the element, otherwise, it will delete.
end
于 2011-07-29T13:54:27.240 回答
20
这就是我对 Rails 5 所做的：
before_destroy do
cannot_delete_with_qrcodes
throw(:abort) if errors.present?
end
def cannot_delete_with_qrcodes
errors.add(:base, 'Cannot delete shop with qrcodes') if qrcodes.any?
end
于 2016-06-17T11:36:05.277 回答
15
Rails 6 的情况：
这有效：
before_destroy :ensure_something, prepend: true do
throw(:abort) if errors.present?
end
private
def ensure_something
errors.add(:field, "This isn't a good idea..") if something_bad
end
validate :validate_test, on: :destroy不起作用：https ://github.com/rails/rails/issues/32376
Since Rails 5 throw(:abort) is required to cancel execution: https://makandracards.com/makandra/20301-cancelling-the-activerecord-callback-chain
prepend: true is required so that dependent: :destroy doesn't run before the validations are executed: https://github.com/rails/rails/issues/3458
You can fish this together from other answers and comments, but I found none of them to be complete.
As a sidenote, many used a has_many relation as an example where they want to make sure not to delete any records if it would create orphaned records. This can be solved much more easily:
has_many :entities, dependent: :restrict_with_error
于 2019-11-25T14:38:50.570 回答
6
ActiveRecord 关联 has_many 和 has_one 允许一个依赖选项，以确保在删除时删除相关的表行，但这通常是为了保持数据库清洁而不是防止它无效。
于 2008-09-23T22:16:49.957 回答
5
您可以将销毁操作包装在控制器中的“if”语句中：
def destroy # in controller context
if (model.valid_destroy?)
model.destroy # if in model context, use `super`
end
end
在哪里valid_destroy？是模型类上的一个方法，如果满足销毁记录的条件，则返回 true。
拥有这样的方法还可以让您阻止向用户显示删除选项 - 这将改善用户体验，因为用户将无法执行非法操作。
于 2008-09-24T05:11:09.743 回答
4
我最终使用此处的代码在 activerecord 上创建了一个 can_destroy 覆盖： https ://gist.github.com/andhapp/1761098
class ActiveRecord::Base
def can_destroy?
self.class.reflect_on_all_associations.all? do |assoc|
assoc.options[:dependent] != :restrict || (assoc.macro == :has_one && self.send(assoc.name).nil?) || (assoc.macro == :has_many && self.send(assoc.name).empty?)
end
end
end
这有一个额外的好处，那就是在 ui 上隐藏/显示删除按钮变得微不足道
于 2013-06-17T19:14:16.860 回答
2
您还可以使用 before_destroy 回调来引发异常。
于 2008-09-23T19:26:17.043 回答
2
我有这些课程或模型
class Enterprise < AR::Base
has_many :products
before_destroy :enterprise_with_products?
private
def empresas_with_portafolios?
self.portafolios.empty?
end
end
class Product < AR::Base
belongs_to :enterprises
end
现在，当您删除企业时，此过程会验证是否有与企业关联的产品 注意：您必须将其写在类的顶部才能首先验证它。
于 2014-01-10T23:00:20.893 回答
1
在 Rails 5 中使用 ActiveRecord 上下文验证。
class ApplicationRecord < ActiveRecord::Base
before_destroy do
throw :abort if invalid?(:destroy)
end
end
class Ticket < ApplicationRecord
validate :validate_expires_on, on: :destroy
def validate_expires_on
errors.add :expires_on if expires_on > Time.now
end
end
于 2017-12-25T12:52:15.037 回答
1
我希望这会得到支持，所以我打开了一个 Rails 问题来添加它：
于 2018-03-29T16:23:56.220 回答