belongs_to with :class_name option fails

Question

I have no idea what went wrong but I can't get belongs_to work with :class_name option. Could somebody enlighten me. Thanks a lot!

Here is a snip from my code.

class CreateUsers < ActiveRecord::Migration     def self.up         create_table :users do |t|             t.text :name         end     end      def self.down         drop_table :users     end end  #####################################################  class CreateBooks < ActiveRecord::Migration     def self.up         create_table :books do |t|             t.text :title             t.integer :author_id, :null => false         end     end      def self.down         drop_table :books     end end  #####################################################  class User < ActiveRecord::Base     has_many: books end  #####################################################  class Book < ActiveRecord::Base     belongs_to :author, :class_name => 'User', :validate => true end  #####################################################  class BooksController < ApplicationController     def create         user = User.new({:name => 'John Woo'})         user.save         @failed_book = Book.new({:title => 'Failed!', :author => @user})         @failed_book.save # missing author_id         @success_book = Book.new({:title => 'Nice day', :author_id => @user.id})         @success_book.save # no error!     end end 

environment:

ruby 1.9.1-p387 Rails 2.3.5

Answer 1

class User < ActiveRecord::Base   has_many :books, :foreign_key => 'author_id' end  class Book < ActiveRecord::Base   belongs_to :author, :class_name => 'User', :foreign_key => 'author_id', :validate => true end 

The best thing to do is to change your migration and change author_id to user_id. Then you can remove the :foreign_key option.

Answer 2

It should be

belongs_to :user, :foreign_key => 'author_id' 

if your foreign key is author id. Since you actually have User class, your Book must belong_to :user.