无法使rails中的关联子对象无效？

Question

我有一个与Trainer和许多Facilities相关联的课程ServiceClasses。我只想在设施和null表中制作参考service_classes，当教练记录被销毁时。

每当我尝试trainer.destroy时，它会向我显示错误，就像我在屏幕截图中提到的那样。 我也尝试过回调来制作参考null before_destroy，但它对我也不起作用。

如果有人可以指导我，请提前感谢，这已经花了我很多时间。

师：

 class Trainer < ActiveRecord::Base
   belongs_to :user
   has_many :service_classes,dependent: :nullify
   has_many :facilities,dependent: :nullify
 end

服务类：

class ServiceClass < ActiveRecord::Base
  acts_as_paranoid
  mount_uploader :image, EventUploader
  belongs_to :trainer
end

设施类：

class Facility < ActiveRecord::Base
  acts_as_paranoid
    belongs_to :user
    belongs_to :facility_category
  has_many :facility_prices
    has_many :facility_details
  belongs_to :trainer
end

架构：

   create_table "service_classes", force: :cascade do |t|
        t.string   "name"
        t.text     "description"
        t.string   "image"
        t.integer  "user_id"
        t.datetime "created_at",                               null: false
        t.datetime "updated_at",                               null: false
        t.datetime "deleted_at"
        t.integer  "trainer_id"
      end

      add_index "service_classes", ["deleted_at"], name: "index_service_classes_on_deleted_at", using: :btree
      add_index "service_classes", ["trainer_id"], name: "index_service_classes_on_trainer_id", using: :btree


 create_table "facilities", force: :cascade do |t|
    t.string   "name"
    t.integer  "user_id"
    t.integer  "facility_category_id"
    t.datetime "created_at",                          null: false
    t.datetime "updated_at",                          null: false
    t.datetime "deleted_at"
    t.integer  "trainer_id"
  end

  add_index "facilities", ["deleted_at"], name: "index_facilities_on_deleted_at", using: :btree
  add_index "facilities", ["trainer_id"], name: "index_facilities_on_trainer_id", using: :btree