【Ruby on Rails】has_many model using jbuilder

Two model as below

group.rb

   1: class Group < ActiveRecord::Base

   2:   has_many :posts

   3:   validates :title,:presence => true

   4: end

post.rb

   1: class Post < ActiveRecord::Base

   2:   belongs_to :group

   3: end

In view/group/index.json.jbuilder

   1: json.groups (@groups) do |group|

   2:   json.extract! group, :id, :title, :description

   3:   json.posts (group.posts) do |post|

   4:    json.extract! post, :id,:comtent

   5:   end

   6: end

So input url on browser,we will get

   1: {

   2:    "groups":[

   3:       {

   4:          "id":1,

   5:          "title":"First",

   6:          "description":"Testtest",

   7:          "posts":[

   8:             {

   9:                "id":1,

  10:                "comtent":"good"

  11:             },

  12:             {

  13:                "id":2,

  14:                "comtent":"test2"

  15:             },

  16:             {

  17:                "id":3,

  18:                "comtent":"test4"

  19:             }

  20:          ]

  21:       }

  22:    ]

  23: }