Rails polymorphic relations - ruby-on-rails

Question

I'm trying to use polymorphic relationship with rails 5.
I have difficulties to figure out how to finish my relations.
I have users, who can take reservations for hotels, restaurants, etc.
My purpose is to get hotels name and reservations when calling /users/{id} through API.
Here is my User model :
class User < ApplicationRecord
has_many :reservations, as: :reservable
has_many :hotels, through: :reservations
end
My Hotel model :
class Hotel < ApplicationRecord
has_many :reservations, as: :reservable
belongs_to :users, through: :reservations
end
My Reservation model :
class Reservation < ApplicationRecord
belongs_to :reservable, polymorphic: true
belongs_to :users
belongs_to :hotels
end
Migrations :
User :
class CreateUsers < ActiveRecord::Migration[5.0]
def change
create_table :users do |t|
t.string :first_name
t.string :last_name
t.string :email
t.timestamps
end
end
end
Reservations :
class CreateReservations < ActiveRecord::Migration[5.0]
def change
create_table :reservations do |t|
t.belongs_to :hotel, index: true
t.belongs_to :user, index: true
t.datetime :date_from
t.datetime :date_to
t.timestamps
end
end
end
class ReservationPolymorphism < ActiveRecord::Migration[5.0]
def change
rename_column :reservations, :hotel_id, :reservable_id
change_column :reservations, :reservable_id, polymorphic: true
add_column :reservations, :reservable_type, :string
end
end
Hotel :
class CreateHotels < ActiveRecord::Migration[5.0]
def change
create_table :hotels do |t|
t.string :name
t.string :address
t.string :postal_code
t.string :town
t.timestamps
end
end
end
I just have 1 line in my reservations table :
mysql> select * from reservations;
+----+---------------+-----------------+---------+---------------------+---------------------+---------------------+---------------------+
| id | reservable_id | reservable_type | user_id | date_from | date_to | created_at | updated_at |
+----+---------------+-----------------+---------+---------------------+---------------------+---------------------+---------------------+
| 1 | 1 | Hotel | 1 | 2017-01-12 00:00:00 | 2017-01-15 00:00:00 | 2016-10-19 09:18:01 | 2016-10-19 09:18:01 |
+----+---------------+-----------------+---------+---------------------+---------------------+---------------------+---------------------+
I have no result when using the API.
Here is what I get, using Rails console :
2.2.3 :001 > thomas = User.find(1)
User Load (0.2ms) SELECT `users`.* FROM `users` WHERE `users`.`id` = 1 LIMIT 1
=> #<User id: 1, first_name: "Thomas", last_name: "Dupont", email: "thomas.dupont#yopmail.com", created_at: "2016-10-18 21:12:12", updated_at: "2016-10-18 21:12:12">
2.2.3 :003 > thomas.reservations
Reservation Load (0.3ms) SELECT `reservations`.* FROM `reservations` WHERE `reservations`.`reservable_id` = 1 AND `reservations`.`reservable_type` = 'User'
2.2.3 :005 > thomas.hotels
NameError: uninitialized constant User::Hotels
So I can see I make basic mistake with rails relations and polymorphism but I really can't find out where I'm wrong.
I think I made a mistake.
I assumed Polymorphism could be use to load other models and their tables (like "morphTo" with eloquent / laravel), whereas it's just to load a model which has no data representation (as described in this post : https://robots.thoughtbot.com/using-polymorphism-to-make-a-better-activity-feed-in-rails )

Answer 1

I guess on viewing your code, you have written extra associations on top of the polymorphic association,
To create a polymorphic association, just the following code is enough. No need to pass extra association inside the model. Please refactor your code as follows,
User model
class User < ApplicationRecord
has_many :reservations, as: :reservable
end
Hotel model :
class Hotel < ApplicationRecord
has_many :reservations, as: :reservable
end
Reservation model :
class Reservation < ApplicationRecord
belongs_to :reservable, polymorphic: true
end
And in the migration file for reservations, add the reservable as below
t.references :reservable, polymorphic: true

Answer 2

Ok i sorted this out :
This is the reservation model :
class Reservation < ApplicationRecord
belongs_to :reservable, polymorphic: true
end
This is the hotel model :
class Hotel < ApplicationRecord
end
And the user model :
class User < ApplicationRecord
has_many :reservations
end
And how I got a results in rails console :
Running via Spring preloader in process 87452
Loading development environment (Rails 5.0.0.1)
2.2.3 :001 > u = User.find(1)
User Load (0.3ms) SELECT `users`.* FROM `users` WHERE `users`.`id` = 1 LIMIT 1
=> #<User id: 1, first_name: "Thomas", last_name: "Dupont", email: "thomas.dupont#yopmail.com", created_at: "2016-10-18 21:12:12", updated_at: "2016-10-18 21:12:12">
2.2.3 :002 > u.reservations
Reservation Load (0.3ms) SELECT `reservations`.* FROM `reservations` WHERE `reservations`.`user_id` = 1
=> #<ActiveRecord::Associations::CollectionProxy [#<Reservation id: 1, reservable_id: 1, reservable_type: "Hotel", user_id: 1, date_from: "2017-01-12 00:00:00", date_to: "2017-01-15 00:00:00", created_at: "2016-10-19 09:18:01", updated_at: "2016-10-19 09:18:01">]>
2.2.3 :003 > u.reservations.first.reservable
Hotel Load (0.3ms) SELECT `hotels`.* FROM `hotels` WHERE `hotels`.`id` = 1 LIMIT 1
=> #<Hotel id: 1, name: "HYATT REGENCY HOTEL", address: "3 Place du Général Kœnig", postal_code: "75017", town: "PARIS", created_at: "2016-10-19 08:36:55", updated_at: "2016-10-19 08:36:55">