Rails使用范圍的“選擇為”嵌套模型

Question

我正在嘗試創建一個Rails作用域，該作用域允許我構造父子模型關聯，如下所示：

{
  id: 1,
  ...other_child_attrs,
  parent: {
    id: 2,
    ...other_parent_attrs
  }
}

我能“注入”的parent在屬性child通過使用以下查詢：

scope :include_parent, -> { Child.joins(:parent).select('childs.*, parents.*') }

問題在於，父級的嵌套屬性在與子級屬性相同的級別上注入（這可能會導致沖突，因為某些子級屬性在child- id ， created_at等中重復）：

{
  id: 2, // Notice there's a parent - child id collision
  ...other_child_attrs,
  ...other_parent_attrs
}

是否可以僅使用活動記錄/普通sql來實現上述結構（而不​​必依賴序列化gem， as_json等）？

Answer 1

試試這個，在模型中使用as_json來做

 def as_json(options={})
     super(:include => { :sales => {
                               :include => { :product => {
                                             :only => [:id,:name, :price] } },
                               :only => :id} })
    end

Answer 2

我認為您過於復雜了。 如果您已經正確配置了兩個具有關聯的模型，那么您已經可以做您想做的事情：

class Child < ActiveRecord::Base
  belongs_to :parent
end

class Parent < ActiveRecord::Base
  has_one :child
end

parent = Parent.create
child = Child.create(parent_id: parent.id)

child.to_json(include: :parent)
 => [{"id":1,"parent_id":1,"created_at":"2017-08-04T20:48:52.056Z","updated_at":"2017-08-04T20:48:52.056Z","parent":{"id":1,"created_at":"2017-08-04T20:47:32.671Z","updated_at":"2017-08-04T20:47:32.671Z"}}]

child = Child.first
child.parent
  Child Load (0.2ms)  SELECT  "children".* FROM "children" ORDER BY "children"."id" ASC LIMIT ?  [["LIMIT", 1]]
  Parent Load (0.1ms)  SELECT  "parents".* FROM "parents" WHERE "parents"."id" = ? LIMIT ?  [["id", 1], ["LIMIT", 1]]
 => #<Parent id: 1, created_at: "2017-08-04 20:47:32", updated_at: "2017-08-04 20:47:32">