通过的has_many协会依赖的所谓谁破坏条件下摧毁 [英] has_many through association dependent destroy under condition of who called destroy

问题描述

有没有一种方法来检查时， before_destroy 挂钩，什么对象（类）呼吁在摧毁 <？ / p>

在下面的例子中，当耐心被破坏，所以他们的约会（这就是我想要的）;但是，我不想让医师如果有任何约会被摧毁与之关联医师。

此外，有没有办法做到在 before_destory 回调这样的检查？如果没有，是否有任何其他的方式来完成的基础上的呼叫（即根据谁的称呼）的方向这种毁灭检查？

 类医师LT; ActiveRecord的::基地
  的has_many：约会，取决于：摧毁
  的has_many：患者，通过：任命
结束
类病人LT; ActiveRecord的::基地
  的has_many：约会，取决于：摧毁
  的has_many：医生通过：任命
结束
任命类LT＆; ActiveRecord的::基地
  belongs_to的：病人
  belongs_to的：医生  before_destroy：ensure_not_referenced_by_anything_important  私人的  高清ensure_not_referenced_by_anything_important
    除非patients.empty？
      errors.add（：基地，这医生不能因为存在约会删除。'）
      假
    结束
  结束
结束
 

解决方案

只是说：

 类医师LT; ActiveRecord的::基地
  的has_many：约会，取决于：restrict_with_exception
  的has_many：患者，通过：任命
结束
 

请注意在相关：restrict_with_exception 。这将导致活动记录拒绝销毁有关联的约会记录的医生记录。

请参阅 API文档和协会基本指南。

Is there a way to check, within a before_destroy hook, what object (class) called destroy?

In the following example, when a patient is destroyed, so are their appointments (which is what I want); however I don't want to allow a physician to be destroyed if there are any appointments associated with that physician.

Again, is there a way to do such a check in the before_destory callback? If not, is there any other way to accomplish this "destruction check" based on the "direction" of the call (i.e. based on who called)?

class Physician < ActiveRecord::Base
  has_many :appointments, dependent: :destroy
  has_many :patients, through: :appointments
end


class Patient < ActiveRecord::Base
  has_many :appointments, dependent: :destroy
  has_many :physicians, through: :appointments
end


class Appointment < ActiveRecord::Base
  belongs_to :patient
  belongs_to :physician

  before_destroy :ensure_not_referenced_by_anything_important

  private

  def ensure_not_referenced_by_anything_important
    unless patients.empty?
      errors.add(:base, 'This physician cannot be deleted because appointments exist.')
      false
    end
  end
end

解决方案

Just say:

class Physician < ActiveRecord::Base
  has_many :appointments, dependent: :restrict_with_exception
  has_many :patients, through: :appointments
end

Note the dependent: :restrict_with_exception. This will cause Active Record to refuse to destroy any Physician records that have associated Appointment records.

See the API docs and the association basics guide.

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