Serialize JSON nested model in Ruby on Rails

Question

I am new to rails and I have two models, one has a foreign key on the other model.

I created a controller and defined and index method which is working fine:

  def index
    @collections = Collection.all
    render json: @collections 
  end

Which is rendering something like this:

[{"id":1,"title":"Collection A","book_id":1,"created_at":"2016-04-10T18:41:32.709Z","updated_at":"2016-04-10T18:41:32.709Z"}]

I would like to transform that book_id field into a list of book objects, something like this:

[{"id":1,"title":"Collection A","books": [{"book_id": 1, "title: "book_title"},],"created_at":"2016-04-10T18:41:32.709Z","updated_at":"2016-04-10T18:41:32.709Z"}]

Then I tried with:

  def index
    @collections = Collection.all
    render :json => collections.as_json(
                  :include => { :book_title }
                )
  end

But is giving me syntax error and I cannot see how to do it properly in this doc http://guides.rubyonrails.org/layouts_and_rendering.html

I am using Rails 4.1.0

Diego Polido Santana · Accepted Answer · 2016-04-10 19:20:13Z

2

Try:

  def index
    @collections = Collection.all
    render :json => @collections.as_json(
                  :include => :book
                )
  end

or if you would like just the :id and :title:

  def index
    @collections = Collection.all
    render :json => @collections.as_json(
                  :include => {:book => {:only => [:id, :title]}}
                )
  end

edited Apr 10, 2016 at 19:20

answered Apr 10, 2016 at 19:08

Diego Polido Santana

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7 Comments

lapinkoira Over a year ago

I tried your first example and it tells me undefined local variable or method `collections' for #<CollectionsController:0x00000003d73680> Did you mean? @collections Then I tried with @collections and it says Did you mean book_id?

Diego Polido Santana Over a year ago

Let me fix my answer

lapinkoira Over a year ago

Hello! with @collections it gives me this error: undefined method `book' for #<Collection:0x00000002df23a0> Did you mean? book_id

Diego Polido Santana Over a year ago

Don't you have belongs_to :book into your Collection class?

lapinkoira Over a year ago

mmm I dont quite understand you, I am new to rails, I created the models this way: bin/rails generate model Book title:string plot:text, bin/rails generate model Collection title:string plot:text book_id:integer

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