如何将两个ActiveRecord查询合并为一个哈希并转换为JSON？

Question

I'm using AJAX to get some results, but the problem is I'm querying two separate models and I want to return both and their relationship to one another as one JSON object.

Here's an example of two models I'm trying to link together -

Car
  belongs_to :user

  :id
  :make
  :year
  :user_id

User
  has_many :cars

  :id
  :first_name
  :last_name
  :birthday

I'm trying to get it to look something like this -

{
  1: {
    id: 1,
    first_name: 'Joe'
    last_name: 'Smith'
    cars: {
      23: {
        id: 23,
        make: 'BMW',
        year: 2009,
        user_id: 1
      },
      24: {
        id: 24,
        make: 'Volvo',
        year: 2012,
        user_id: 1
      }
    }
  },
  2: {
    id: 2,
    first_name: 'Bob'
    last_name: 'Johnson'
    cars: {
      35: {
        id: 35,
        make: 'Ford',
        year: 2013,
        user_id: 2
      }
    }
  }
}

Answer 1

Create a new (private) method in your controller:

def format_json(users)
  result = {}
  users.each do |user|
    result[user.id] = user.formatted_data
  end
  return result
end

Change the action to return:

users = Users.includes(:cars).where("<your_where_clause>").limit(<n>)
render :json => { :result => format_json(users) }.to_json

app/models/user.rb

class User < ActiveRecord::Base

  def formatted_data
    {
      :id         => self.id,
      :first_name => self.first_name,
      :last_name  => self.last_name,
      :cars       => self.get_car_info
    }
  end

  def get_car_info
    car_info = {}
    self.cars.each do |car|
      car_info[car.id] = car.info
    end
    return car_info
  end
end

app/models/car.rb

class Car < ActiveRecord::Base
  def info
    {
      :id      => self.id,
      :make    => self.make,
      :year    => self.year,
      :user_id => self.user_id
    }
  end
end

Answer 2

I ended up using the .as_json I found detailed here to convert ActiveRecord to a plain Ruby hash and passed that hash to the view.

user = User.find(params[:user_id].to_i)

@json = {}
@json[user.id] = user.as_json
@json[user.id]['cars'] = {}

user.cars.each do |car|
  @json[user.id]['cars'][car.id] = car.as_json
end

render json: { status: true, users: @json }