ruby-on-rails - 如何在 Mongoid 中保存 embeds_many 关系？

Question

class Hotel
  include Mongoid::Document

  field :title, type: String

  embeds_many :comments
end

class Comment
  include Mongoid::Document

  field :text, type: String

  belongs_to :hotel

  validates :text, presence: true
end

h = Hotel.create('hotel') 

   => <#Hotel _id: 52d68dd47361731d8b000000, title: "hotel">

c = Comment.new(text: 'text')

   => <#Comment _id: 52d68f3d7361731d8b040000, text: "text", hotel_id: nil>

h.comments << c

   => [#<Comment _id: 52d68f3d7361731d8b040000, text: "text", hotel_id: nil>]
h.save

   => true
Hotel.last.comments

   => []

变体2

h.comments << Comment.new(text: 'new', hotel_id: h.id)

   => [<#Comment _id: 52d68f3d7361731d8b040000, text: "text", hotel_id: nil>, <#Comment _id: 52d691e17361731d8b050000, text: "new", hotel_id: BSON::ObjectId('52d68dd47361731d8b000000')>]

h.save

   => true
Hotel.last.comments

   => []

Answer 1

我看到两个可能的问题:

Hotel.last不一定Hotel 52d68dd47361731d8b000000。你应该看看h.comments或偏执，h.reload和 h.comments .

你的联想很困惑。

来自 fine manual :

Embedded 1-n

One to many relationships where the children are embedded in the parent document are defined using Mongoid's embeds_many and embedded_in macros.

Defining

The parent document of the relation should use the embeds_many macro to indicate it has n number of embedded children, where the document that is embedded uses embedded_in.

所以你的关系应该这样定义:

class Hotel
  embeds_many :comments
end

class Comment
  embedded_in :hotel
end

您正在使用 belongs_to: hotel在 Comment什么时候该说 embedded_in :hotel .

文档还说:

Definitions are required on both sides to the relation in order for it to work properly.

并且您的关系在一侧配置不正确，因此无法正常工作。