ActiveRecord return nested JSON data from DB

Question

I have 4 database tables in Postgres. course, activity, lesson and task.

Currently when I do Course.find_by_id(params[:id])in my controller the models are setup to return all lessons in a course, but I'd like this nesting to extend to the activities in the lesson and include the one-to-one relationship of task to activity too.

class Course < ActiveRecord::Base
  validates :title, uniqueness: { case_sensitive: false }, presence: true

  has_many :lessons, -> { order(position: :asc) }, dependent: :restrict_with_error
  belongs_to :subject

  accepts_nested_attributes_for :lessons
end


class Lesson < ActiveRecord::Base
  validates :title, uniqueness: { case_sensitive: false }, presence: true
  validates :position, uniqueness: { scope: :course_id }, presence: true

  belongs_to :course
  has_many :activities, dependent: :restrict_with_error
  acts_as_list column: :position, scope: :course

  accepts_nested_attributes_for :course
end


class Activity < ActiveRecord::Base
  validates :name, uniqueness: { case_sensitive: false }, presence: true
  validates :task, presence: true
  validates :term, presence: true

  belongs_to :lesson
  belongs_to :term
  has_one :task, dependent: :destroy

  accepts_nested_attributes_for :task, allow_destroy: true

  attr_accessor :taskable_attributes
end

class Task < ActiveRecord::Base
  validates :name, uniqueness: { case_sensitive: false }, presence: true
  validates :taskable, presence: true

  belongs_to :activity
  belongs_to :taskable, polymorphic: true, dependent: :destroy

  accepts_nested_attributes_for :taskable, allow_destroy: true
end

My JSON output currently looks like this:

{
    "id": 1,
    "title": "Algebra",
    "description": "Do you know your y times table?",
    "subject_id": 1,
    "lessons": [
        {
            "id": 1,
            "title": "Functions",
            "description": "A mapping of inputs to outputs",
            "position": 2,
            "course_id": 1
        }
    ]
}

But I would like it to contain more nested data

{
    "id": 1,
    "title": "Algebra",
    "description": "Do you know your y times table?",
    "subject_id": 1,
    "lessons": [
        {
            "id": 1,
            "title": "Functions",
            "description": "A mapping of inputs to outputs",
            "position": 2,
            "course_id": 1,
            "activities": [
                {
                   "id": 1,
                   "title": "Activity 1"
                   "task": 
                       {
                           "id": 1,
                           "name": "Task name here"
                       }
               }
            ]
        }
    ]
}

I've never used ruby or ruby on rails before, but being able to add this nesting to the frontend app until our rails developer returns would make my job a lot easier.

zauzaj · Accepted Answer · 2017-08-10 10:52:50Z

4

you can try in your responsible controller something like:

render json: @course.to_json( { include: [ lessons: { include: { :task } } ] } )

You can also exclude fields from any association with only, also you can include some methods with methods:{}

Cheers

answered Aug 10, 2017 at 10:52

zauzaj

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1 Comment

Cobolt Over a year ago

My final solution was: render json: Course.all.to_json( { include: [ lessons: { include: [ activities: { include: :task } ] } ] } )

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