没有ID的用户无法找到-Ruby 2.1.4 / Rails 4.1.6

Question

I am facing an error while trying to link the :username in my User table and my Room table. I made a custom auth with devise and added :username .

I would like the username to be the link between the User table from devise and my Room table.

I am trying to build this app to recreate a kind of airbnb but mainly as an exercise as I started programming in ruby few months ago.

I get the error:

ActiveRecord::RecordNotFound in RoomsController#new
Couldn't find User without an ID
line #19 @room.username = User.find(params[:username])

Thank you very much for your help. I am stuck in here for hours now :-(

rooms_controller

def new
  @room = Room.new
  @room.username = User.find(params[:username]) #error seems to come from here
end

routes.rb

Rails.application.routes.draw do
  devise_for :users
  get "home/info"

  root :to => "home#info"

  resources :rooms

  resources :users do
  resources :rooms
end

room.rb

class Room < ActiveRecord::Base
  mount_uploader :photo, PictureUploader
  belongs_to :user
  validates_presence_of :username, :location, :description, :capacity, :price_day, :photo
end

user.rb

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable
  validates_presence_of :username
  validates_uniqueness_of :username

  has_many :rooms
end

Answer 1

It should be something like this

def new
  @room = Room.new
  @room.username = User.find_by_username(params[:username])
end

If you just use .find() it expects the id of the user. Also see http://guides.rubyonrails.org/active_record_querying.html#dynamic-finders

Answer 2

There is a logic error in that you are saving @room.username to the User Object. You should be setting @room.user = User.find_by(...) OR @room.user_id = User.find_by(...).id

Active record will automagically make a method for you that will be @room.user.username if you want to get the username.

Now, here are the ways to find a user.

@room = Room.new #Then either of the following

@room.user = User.find_by(username: params[:username]) #Returns only one value

@room.user = User.find_by_username(params[:username])  #Returns only one value

@room.user = User.where(username: params[:username])   #Returns all users which meet condition.

As already mentioned in the answers, User.find() takes an ID. One thing to know is that all methods that start with .find for active record return a single record even if many meet the condition.

If you are having any problems still, then show us your Database Schema, and we can help further.

Answer 3

I found a solution. The Room is created with the the right :username and nothing is seen by the user. In my Rooms controller, I kept

def new
@room = Room.new end

And I added this line in the "def create" part :

def create
@room = Room.new(room_params)
@room.username = current_user.username

Thank you for your help, this help me to understand better the relations in rails.

Have a nice day !