advanced_ar.rb

require 'active_record'

def setup
  ActiveRecord::Base.establish_connection adapter: "sqlite3", database: ":memory:"
end

def generate_migrations
  ActiveRecord::Migration.create_table :hotels do |t|
    t.string :name
    t.integer :room_count
    t.timestamps
  end

  ActiveRecord::Migration.create_table :rooms do |t|
    t.belongs_to :hotel
    t.integer :rate
    t.timestamps
  end

  ActiveRecord::Migration.create_table :bookings do |t|
    t.belongs_to :room
    t.belongs_to :user
    t.datetime :checkin
    t.datetime :checkout
    t.integer :rate

    t.timestamps
  end

  ActiveRecord::Migration.create_table :users do |t|
    t.string :name
    t.timestamps
  end

  ActiveRecord::Migration.create_table :ratings do |t|
    # Since we want multiple things to be rateable
    # (hotels and rooms) we define the columns necessary
    # for a polymorphic association (_id and _type)
    t.integer :rateable_id
    t.string :rateable_type

    t.text :text
    t.timestamps
  end

  # Here's an example of what the ratings table looks like after we create a
  # few records.
  #  id      rateable_id     rateable_type         text
  #  1       1               "Hotel"               "Great food."
  #  2       1               "Room"                "Wish there was a bed!"

end

def migrate
  ActiveRecord::Migrator.up "db/migrate"
end

setup()
generate_migrations()
migrate()

class Hotel < ActiveRecord::Base
  has_many :rooms
  has_many :bookings, through: :rooms
  has_many :booked_guests, through: :bookings, source: :guest
  has_many :ratings, as: :rateable

  def to_s
    "#{name} with #{rooms.count} rooms"
  end
end

class Booking < ActiveRecord::Base
  belongs_to :room
  belongs_to :guest, class_name: "User", foreign_key: "user_id"
end

class Room < ActiveRecord::Base
  belongs_to :hotel
  has_many :bookings
  has_many :ratings, as: :rateable
end

class User < ActiveRecord::Base
  has_many :bookings
  has_many :booked_rooms, through: :bookings, source: :room
end

class Rating < ActiveRecord::Base
  belongs_to :rateable, polymorphic: true
end

hotel = Hotel.create!(name: "Westin", room_count: 200)
hotel.rooms << Room.create!(rate: 200)
hotel.rooms << Room.create!(rate: 50)

puts Room.first.hotel

user = User.create!(name: "John Smith")
room = hotel.rooms.first
b = Booking.create!(guest: user, room: room)

room_rating = Rating.create!(rateable: room, text: "Wish there was a bed!")
hotel_rating = Rating.create!(rateable: hotel, text: "Food is great!")

p room_rating.rateable
p hotel_rating.rateable