Serializing deeply nested associations with active_model_serializers

Question

I\'m using Rails 4.2.1 and active_model_serializers 0.10.0.rc2

I\'m new to API\'s and chose active_model_serializers because i

Answer 1

This should do what you're looking for.

@project.to_json( include: { estimates: { include: {:project, :project_code, :tax_type, :proposals } } } )

The top level nesting will be automatically included, but anything deeper than that will need to be included in your show action or wherever you are calling this.

Answer 2

Per commit 1426: https://github.com/rails-api/active_model_serializers/pull/1426 - and related discussion, you can see that the default nesting for json and attributes serialization is one level.

If you want deep nesting by default, you can set a configuration property in an active_model_serializer initializer:

ActiveModelSerializers.config.default_includes = '**'

For detailed reference from v0.10.6: https://github.com/rails-api/active_model_serializers/blob/v0.10.6/docs/general/adapters.md#include-option

Answer 3

In my case I created a file called 'active_model_serializer.rb' placed at 'MyApp/config/initializers' with the following content:

ActiveModelSerializers.config.default_includes = '**'

Do not forget to restart the server:

$ rails s

Answer 4

You can change default_includes for the ActiveModel::Serializer:

# config/initializers/active_model_serializer.rb
ActiveModel::Serializer.config.default_includes = '**' # (default '*')

In addition, in order to avoid infinite recursion, you can control the nested serialization follows:

class UserSerializer < ActiveModel::Serializer
  include Rails.application.routes.url_helpers

  attributes :id, :phone_number, :links, :current_team_id

  # Using serializer from app/serializers/profile_serializer.rb
  has_one :profile
  # Using serializer described below:
  # UserSerializer::TeamSerializer
  has_many :teams

  def links
    {
      self: user_path(object.id),
      api: api_v1_user_path(id: object.id, format: :json)
    }
  end

  def current_team_id
    object.teams&.first&.id
  end

  class TeamSerializer < ActiveModel::Serializer
    attributes :id, :name, :image_url, :user_id

    # Using serializer described below:
    # UserSerializer::TeamSerializer::GameSerializer
    has_many :games

    class GameSerializer < ActiveModel::Serializer
      attributes :id, :kind, :address, :date_at

      # Using serializer from app/serializers/gamers_serializer.rb
      has_many :gamers
    end
  end
end

Result:

{
   "user":{
      "id":1,
      "phone_number":"79202700000",
      "links":{
         "self":"/users/1",
         "api":"/api/v1/users/1.json"
      },
      "current_team_id":1,
      "profile":{
         "id":1,
         "name":"Alexander Kalinichev",
         "username":"Blackchestnut",
         "birthday_on":"1982-11-19",
         "avatar_url":null
      },
      "teams":[
         {
            "id":1,
            "name":"Agile Season",
            "image_url":null,
            "user_id":1,
            "games":[
               {
                  "id":13,
                  "kind":"training",
                  "address":"",
                  "date_at":"2016-12-21T10:05:00.000Z",
                  "gamers":[
                     {
                        "id":17,
                        "user_id":1,
                        "game_id":13,
                        "line":1,
                        "created_at":"2016-11-21T10:05:54.653Z",
                        "updated_at":"2016-11-21T10:05:54.653Z"
                     }
                  ]
               }
            ]
         }
      ]
   }
}

Answer 5

If you are using the JSONAPI adapter you can do the following to render nested relationships:

render json: @project, include: ['estimates', 'estimates.project_code', 'estimates.tax_type', 'estimates.proposals']

You can read more from the jsonapi documentation:http://jsonapi.org/format/#fetching-includes

Answer 6

So this my not be the best or even a good answer, but this is working how I need it to.

While including nested and side-loaded attributes appears to be supported when using the json_api adapter with AMS, I needed support for flat json. In addition, this method worked well because each serializer is specifically generating exactly what I need it to independent of any other serializer and without having to do anything in the controller.

Comments / alternate methods are always welcome.

Project Model

class Project < ActiveRecord::Base      
  has_many  :estimates, autosave: true, dependent: :destroy
end

ProjectsController

def index
  @projects = Project.all
  render json: @projects
end

ProjectSerializer

class ProjectSerializer < ActiveModel::Serializer
  attributes  :id, 
              :name,
              :updated_at,

              # has_many
              :estimates



  def estimates
    customized_estimates = []

    object.estimates.each do |estimate|
      # Assign object attributes (returns a hash)
      # ===========================================================
      custom_estimate = estimate.attributes


      # Custom nested and side-loaded attributes
      # ===========================================================
      # belongs_to
      custom_estimate[:project] = estimate.project.slice(:id, :name) # get only :id and :name for the project
      custom_estimate[:project_code] = estimate.project_code
      custom_estimate[:tax_type] = estimate.tax_type

      # has_many w/only specified attributes
      custom_estimate[:proposals] = estimate.proposals.collect{|proposal| proposal.slice(:id, :name, :updated_at)}

      # ===========================================================
      customized_estimates.push(custom_estimate)
    end

    return customized_estimates
  end
end

Result

[
  {
    "id": 1,
    "name": "123 Park Ave.",
    "updated_at": "2015-08-09T02:36:23.950Z",
    "estimates": [
      {
        "id": 1,
        "name": "E1",
        "release_version": "v1.0",
        "exchange_rate": "0.0",
        "created_at": "2015-08-12T04:23:38.183Z",
        "updated_at": "2015-08-12T04:23:38.183Z",
        "project": {
          "id": 1,
          "name": "123 Park Ave."
        },
        "project_code": {
          "id": 8,
          "valuation": 30,
          "created_at": "2015-08-09T18:02:42.079Z",
          "updated_at": "2015-08-09T18:02:42.079Z"
        },
        "tax_type": {
          "id": 1,
          "name": "No Tax",
          "created_at": "2015-08-09T18:02:42.079Z",
          "updated_at": "2015-08-09T18:02:42.079Z"
        },
        "proposals": [
          {
            "id": 1,
            "name": "P1",
            "updated_at": "2015-08-12T04:23:38.183Z"
          },
          {
            "id": 2,
            "name": "P2",
            "updated_at": "2015-10-12T04:23:38.183Z"
          }
        ]
      }
    ]
  }
]

I basically disregarded trying to implement any has_many or belongs_to associations in the serializers and just customized the behavior. I used slice to select specific attributes. Hopefully a more elegant solution will be forth coming.