Question

i am using devise to register and authenticate users.What i am trying to acomplish is for a user to sign in and be able to add a book in his profile.And later when he sign back in the book will be shown.So in my application i have user model and book model.But i am having a problem accessing user in one of the controller.I am getting a exception undefined method `books’ for nil:NilClass.

VIEW

Home#index

   <p >Welcome to the new generation</p>
    <p><%= link_to "Add new Book",:controller =>"book", :action => 'new' %></p>
   <% @books.each do |b| %>
  <p><%= b.author%></p>
 <p><%= b.title%></p>
 <%end%>

HOME CONTROLLER

class HomeController < ApplicationController
 def index
 @user = current_user
 @user.books||=Book.new
 @books=@user.books
end
end

BOOK CONTROLLER

class BookController < ApplicationController
 def new
@books = Book.new
# redirect_to :controller=>"home" ,:action=>"index"
end

 def create
 @books = Book.new(params[:book])
  if @books.save
    render "home/index"
       #redirect_to :controller=>"home" ,:action=>"index"
  else

        render :action => 'new'
  end
end

BOOK VIEW

<h1>Book#new</h1>

 <%= form_for(:book) do |f| %>
  <p><%= f.text_field :title %></p>
  <p><%= f.text_field :author %></p>
  <p><%= f.submit "Add book"%> 

BOOK MODEL

class Book < ActiveRecord::Base
belongs_to :user
end

USER MODEL

class User < ActiveRecord::Base
has_many :books
# Include default devise modules. Others available are:
# :token_authenticatable, :lockable, :timeoutable and :activatable
devise :database_authenticatable, :registerable,
     :recoverable, :rememberable, :trackable, :validatable

# Setup accessible (or protected) attributes for your model
attr_accessible :email, :password,         :password_confirmation,:firstname,:lastname,:school,:major,:sex,:zipcode


 end

ROUTE

 Campus::Application.routes.draw do


 get "book/index"

 get "book/edit"

  get "book/new"

  get "home/edit"

  devise_for :users
  resources :book     
  root :to=> "home#index"
  match '/book/new' =>"home#index"
   end

CREATE TABLE

class CreateBooks < ActiveRecord::Migration
  def self.up
create_table :books do |t|
  t.text :title
  t.text :author
  t.integer :user_id, :null => false
  t.timestamps
 end
   add_foreign_key(:books, :users)
 end

def self.down
drop_table :books
remove_foreign_key(:books, :users)
end
end

DB SCHEMA

  ActiveRecord::Schema.define(:version => 20110609055608) do

  create_table "books", :force => true do |t|
  t.text     "title"
  t.text     "author"
  t.datetime "created_at"
  t.datetime "updated_at"
  end

  create_table "courses", :force => true do |t|
  t.string   "name"
  t.datetime "created_at"
  t.datetime "updated_at"
  end

  create_table "strong_ins", :force => true do |t|
  t.string   "subject"
  t.string   "topic"
  t.text     "description"
  t.datetime "created_at"
  t.datetime "updated_at"
  end

  create_table "users", :force => true do |t|
  t.string   "email",                               :default => "", :null => false
  t.string   "encrypted_password",   :limit => 128, :default => "", :null => false
  t.string   "password_salt",                       :default => "", :null => false
  t.string   "reset_password_token"
  t.string   "remember_token"
  t.datetime "remember_created_at"
  t.integer  "sign_in_count",                       :default => 0
  t.datetime "current_sign_in_at"
  t.datetime "last_sign_in_at"
  t.string   "current_sign_in_ip"
  t.string   "last_sign_in_ip"
  t.datetime "created_at"
  t.datetime "updated_at"
  t.string   "firstname"
  t.string   "lastname"
  t.text     "school"
  t.text     "major"
  t.string   "sex"
  t.integer  "zipcode"
 end

  add_index "users", ["email"], :name => "index_users_on_email", :unique => true
  add_index "users", ["reset_password_token"], :name =>      "index_users_on_reset_password_token", :unique => true

  create_table "weak_ins", :force => true do |t|
   t.string   "subject"
   t.string   "topic"
   t.text     "description"
   t.datetime "created_at"
   t.datetime "updated_at"
   end

   end

Answer 1

To get the currently logged in user in controllers using devise you simply use the current_user variable. Also, the relationship between User and Book is has_many :books so current_user.book doesn’t exist.

class HomeController < ApplicationController
 def index
  @user = current_user
  @books = @user.books
 end
end