在下面的例子中,当一个病人被摧毁时,他们的约会也是如此(这就是我想要的);但是,如果有任何与该医生相关的预约,我不想让医生被销毁.

再次,有没有办法在before_destory回调中进行这样的检查？如果没有,是否还有其他方法可以根据通话的“方向”(即根据谁打电话)完成“破坏检查”？

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