Question

设定：

可以为预订分配多个资源。预留资源组合可以有多个SetUps。

我尝试设置这样的模型：

yarn server
yarn run v1.5.1
$ lerna exec --scope @amplifactory/server -- nodemon --exec "babel-node start-server.js
lerna info version 2.9.0
lerna info scope @amplifactory/server
[nodemon] 1.17.2
[nodemon] to restart at any time, enter `rs`
[nodemon] watching: *.*
[nodemon] starting `babel-node start-server.js`
D:\monorepo\node_modules\babel-core\lib\transformation\file\options\option-manager.js:328
        throw e;
        ^

Error: Couldn't find preset "@babel/es2017" relative to directory "D:\\9. DEV\\WORKSPACE\\amplifactory\\packages\\server"
    at D:\monorepo\node_modules\babel-core\lib\transformation\file\options\option-manager.js:293:19
    at Array.map (native)
    at OptionManager.resolvePresets (D:\monorepo\node_modules\babel-core\lib\transformation\file\options\option-manager.js:275:20)
    at OptionManager.mergePresets (D:\monorepo\node_modules\babel-core\lib\transformation\file\options\option-manager.js:264:10)
    at OptionManager.mergeOptions (D:\monorepo\node_modules\babel-core\lib\transformation\file\options\option-manager.js:249:14)
    at OptionManager.init (D:\monorepo\node_modules\babel-core\lib\transformation\file\options\option-manager.js:368:12)
    at compile (D:\monorepo\node_modules\babel-register\lib\node.js:103:45)
    at loader (D:\monorepo\node_modules\babel-register\lib\node.js:144:14)
    at Object.require.extensions.(anonymous function) [as .js] (D:\monorepo\node_modules\babel-register\lib\node.js:154:7)
    at Module.load (module.js:487:32)
[nodemon] app crashed - waiting for file changes before starting...

步骤：

创建预订，分配资源，有效：

class SetUp < ApplicationRecord
  has_many :reservation_resource_set_ups, dependent: :destroy
  has_many :reservations, through: :reservation_resource_set_ups
  has_many :resources, through: :reservation_resource_set_ups
end

class Resource < ApplicationRecord
  has_many :reservation_resources, dependent: :destroy
  has_many :reservation_resource_set_ups, dependent: :destroy
  has_many :reservations, through: :reservation_resources
  has_many :set_ups, through: :reservation_resource_set_ups
end

class Reservation < ApplicationRecord
  has_many :reservation_resources, dependent: :destroy
  has_many :reservation_resource_set_ups, dependent: :destroy
  has_many :resources, through: :reservation_resources
  has_many :set_ups, through: :reservation_resource_set_ups
end

class ReservationResource < ApplicationRecord
  belongs_to :reservation
  belongs_to :resource
  has_many :reservation_resource_set_ups
  has_many :set_ups, through: :reservation_resource_set_ups
end

class ReservationResourceSetUp < ApplicationRecord
  belongs_to :reservation
  belongs_to :resource
  belongs_to :set_up
end

reservation和reservation_resources表格已正确更新。

将设置分配给reservation_resource，失败：
```
res1 = Reservation.create(name:"res name")
res1.resources << Resource.find(1)  # resource with id = 1 exists
```
此操作失败，错误为res1.resources.first.set_ups << SetUp.find(1) # set_ups with id = 1 exists

你能指点我正确的方向吗？谢谢！

（这是架构，如果有用......）

ActiveRecord::RecordInvalid (Validation failed: Reservation must exist)

Answer 1

＆LT;＆LT;当您需要设置多个外键时，方法无用。

集合＆lt;＆lt;方法通过将其外键设置为调用模型的主键，将一个或多个对象添加到集合中。

所以你要对待代码

res1.resources.first.set_ups << SetUp.find(1) # set_ups with id = 1 exists

作为

ReservationResourceSetUp.create(
  set_up: SetUp.find(1), # from << SetUp.find(1)
  resource: res1.resources.first, # from left side
  reservation: nil # raises the error
)

要创建条目，只需指定所有键：

ReservationResourceSetUp.create(
  set_up: SetUp.find(1),
  resource: res1.resources.first,
  reservation: res1
)

Answer 2

您的模型存在一些问题。例如：

ReservationResource has_many :reservation_resource_set_ups。 ActiveRecord假定ReservationResourceSetUp中的reservation_resource_id

但是

ReservationResourceSetUp不belongs_to :reservation_resource

我建议您对模型进行一些更改：

class Resource < ApplicationRecord
  has_many :reservation_resources, dependent: :destroy
  has_many :reservations, through: :reservation_resources
  has_many :reservation_resource_set_ups, through: :reservation_resources
  has_many :set_ups, through: :reservation_resource_set_ups
end

class Reservation < ApplicationRecord
  has_many :reservation_resources, dependent: :destroy
  has_many :resources, through: :reservation_resources
  has_many :reservation_resource_set_ups, through: :reservation_resources
  has_many :set_ups, through: :reservation_resource_set_ups
end

class ReservationResource < ApplicationRecord
  belongs_to :reservation
  belongs_to :resource
  has_many :reservation_resource_set_ups
  has_many :set_ups, through: :reservation_resource_set_ups
end

class SetUp < ApplicationRecord
  has_many :reservation_resource_set_ups, dependent: :destroy
  has_many :reservations_resources, through: :reservation_resource_set_ups
  has_many :resources, through: :reservation_resources
  has_many :reservations, through: :reservation_resources
end

class ReservationResourceSetUp < ApplicationRecord
  belongs_to :reservation_resource
  belongs_to :set_up
end

主要的变化是ReservationResourceSetUp现在属于ReservationResource和SetUp（而不是Reservation，Resource和SetUp）。在实践中它是一样的，但我认为它以更好的方式处理你的情况。首先为资源创建预留。然后为此ReservationResource分配一个或多个SetUps。我认为如果您进行这些更改，您的代码将会起作用。您当然必须更改迁移。现在您的ReservationResourceSetUp将有一个reservation_resource_id和一个set_up_id。

使用嵌套的has_many关联在模型中创建数据库条目时出错

2 个答案: