How to get fields from has_many :throught association

Question

I have a many-to-many association throught RoomsUsers model and in this model i have a role field, association works well but i can't access this field. My schema looks like:

 create_table "messages", force: :cascade do |t|
   t.text "body"
   t.datetime "created_at", null: false
   t.datetime "updated_at", null: false
   t.integer "user_id"
   t.integer "room_id"
 end                                                                       
 create_table "rooms", force: :cascade do |t|
   t.string "name"
   t.datetime "created_at", null: false
   t.datetime "updated_at", null: false
   t.integer "rooms_user_id"
 end
 create_table "rooms_users", force: :cascade do |t|
   t.integer "user_id"
   t.integer "room_id"
   t.datetime "created_at", null: false
   t.datetime "updated_at", null: false
   t.string "role"
   t.integer "last_checked"
 end
create_table "users", force: :cascade do |t|
  t.string "name"
  t.string "password_digest"
  t.datetime "created_at", null: false
  t.datetime "updated_at", null: false
  t.string "mail"
  t.integer "rooms_user_id"
end

User model:

class User < ApplicationRecord
  has_secure_password(validations: false)
  has_many :messages
  has_many :rooms_users
  has_many :rooms, through: :rooms_users
  accepts_nested_attributes_for :rooms_users
  attr_accessor :register, :mail_confirmation, :login
end

Room model:

class Room < ApplicationRecord
  has_many :rooms_users
  has_many :users, through: :rooms_users
  accepts_nested_attributes_for :rooms_users
  has_many :message
end

RoomsUsers model:

class RoomsUsers < ApplicationRecord
  belongs_to :user
  belongs_to :room
end

And i am trying to get role field from first user's room.

User.first.rooms.first.role

It give's me NoMethodError (undefined method `role' for #). What's wrong?

model name must be `RoomsUser` instead of `RoomsUsers` as per convention. — ray, Jan 05 '19 at 11:22
Ruby on Rails follow **linguistic convention**. That means a model represents a single user, whereas a database table consists of many users. So model name is singular & controller name is always plural. — ray, Jan 05 '19 at 11:31
It is not about working, it is about more than that. Code must be clean, readable, following convention and lots of things. — ray, Jan 05 '19 at 11:33
Are you sure that your first user has any room? How did you check that? — spickermann, Jan 05 '19 at 12:08

score 1 · Answer 1 · answered Jan 05 '19 at 13:09

1

You're trying to access role field in the rooms table, but it is in rooms_users table. Should be:

User.first.rooms_users.first.role

And remove rooms_user_id from rooms and users table, you don't need it

answered Jan 05 '19 at 13:09

Vasilisa

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score 0 · Answer 2 · answered Jan 05 '19 at 19:44

If you want to access "role" field through Rooms model, you will need to change the place of your "role" field from rooms_users table to rooms table. Doing it you can access "role" using User.first.rooms.first.role.

However if you want to keep "role" field in rooms_users table, so you will need to use User.first.rooms_users.first.role as Vasilisa has already mentioned.

t.integer "rooms_user_id" are not necessary in rooms and users tables. The has_many used in rooms and users are already linking rooms_users with them.

How to get fields from has_many :throught association

2 Answers2