Rails使用范围的“选择为”嵌套模型

Question

I'm trying to create a Rails scope which allows me to structure a parent - child model association as follows:

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

I was able to 'inject' the parent attributes in the child by using the following query:

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

The issue is that the nested attributes of the parent are injected at the same level as the child attributes (which might cause collisions as some of the child attributes are repeated in the child - id , created_at , etc):

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

Is it possible to achieve the structure explained above with active record/ plain sql alone (without having to rely on serialize gem, as_json , etc)?

Answer 1

try this, do it using as_json in the model

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

Answer 2

I think that you are over-complicating this. If you have two models properly configured with associations then you can already do what you want to do:

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">