在表中添加外键

Question

我一直收到这个异常："SQLite3::SQLException: no such column: books.user_id: SELECT "books".* FROM "books" WHERE ("books".user_id = 4)"。听起来就像是在books表中没有user_id字段。

所以我刚刚安装了Foreigner插件，并在book迁移文件中添加了"t.integer :user_id, :null => false"和"add_foreign_key(:books, :users)"。我运行了"rake db:migrate"，但仍然出现相同的异常。

我正在使用Windows中的Rails 3和Devise进行用户认证。

主页视图

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

主页控制器

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

图书控制器

    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

创建表/图书迁移

  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

图书视图

<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"%> 

书籍模型

 class Book < ActiveRecord::Base
 belongs_to :user
 end

用户模型

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

路由 Campus::Application.routes.draw do 获取 "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

数据库结构

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

  create_table "books", :force => true do |t|
    t.text     "title"
    t.text     "author"
    t.integer  "user_id",    :null => false
    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

- katie

Answer 1

运行迁移后，user_id列应该出现在模式中。由于它没有出现在您的列表中，所以我认为这就是问题所在。确保rake db:migrate没有错误。如果需要，您可以使用rake db:rollback && rake db:migrate重新执行迁移。

- zetetic

---

我刚刚运行了rake db:rollback，然后再次运行rake db:migrate，但仍然出现相同的异常。 - katie

你能检查一下 log/development.log 文件，看看 SQL 语句是否被记录了吗？ - zetetic

说起来， foreigner 可能不适用于 SQLite。尝试移除 add_foreign_key 语句并再次运行迁移。 - zetetic

好的，我已经成功添加了外键，但是在Home/index视图中书籍没有出现。这是dev.log文件中的信息：Load (3.0ms)[0m SELECT "users".* FROM "users" WHERE "users"."id" = 4 LIMIT 1 [1m[36mBook Load (1.0ms)[0m [1mSELECT "books".* FROM "books" WHERE ("books".user_id = 4)[0m - katie