Question

I have three models:

class A < ActiveRecord::Base
  has_many :bs
end

class B < ActiveRecord::Base
  has_one :c
  belongs_to :a
end

class C < ActiveRecord::Base
  belongs_to :b
end

I want to get json data containing all B’s and C’s for an A. I tried a number of things similar to:

render json: @as, :include => [:bs => [:include=>[:c]]

but nothing works. What would be a good way to do this.

Answer 1

Refer to ActiveModel::Serializers::JSON#as_json to see the options you can pass to render :json. To quote:

To include associations use :include …

Second level and higher order associations work as well:

user.as_json(:include => { :posts => {
                             :include => { :comments => {
                                             :only => :body } },
                             :only => :title } })
# => { "id": 1, "name": "Konata Izumi", "age": 16,
#      "created_at": "2006/08/01", "awesome": true,
#      "posts": [ { "comments": [ { "body": "1st post!" }, { "body": "Second!" } ],
#                   "title": "Welcome to the weblog" },
#                 { "comments": [ {"body": "Don't think too hard" } ],
#                   "title": "So I was thinking" } ]
#    }

It’s not necessary to call to_json or as_json directly, as render :json does it automatically.