has_many通过关联依赖destroy条件下谁调用destroy [英] has_many through association dependent destroy under condition of who called destroy

问题描述

有没有办法在 before_destroy 钩子中检查称为 destroy 的对象(类)?

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

在下面的例子中，当一个 patient 被销毁时，他们的 appointments 也会被销毁(这是我想要的)；但是，如果有任何与 physician 相关的 appointments，我不想让 physician 被销毁.

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.

再说一次，有没有办法在 before_destory 回调中进行这样的检查?如果没有，有没有其他方法可以根据呼叫的方向"(即根据呼叫者)来完成这种破坏检查"?

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

推荐答案

就说:

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

注意dependent: :restrict_with_exception.这将导致 Active Record 拒绝销毁任何与约会记录相关联的医师记录.

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

请参阅API文档和协会基础指南.

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