Question

I have the following models:

class User < ActiveRecord::Base
  has_many :books, :dependent => :destroy
  has_many :favorites
  has_many :books, :through => :favorites
end

class Favorite < ActiveRecord::Base
  belongs_to :book
  belongs_to :user

  validates :user_id, :book_id, :presence => true
end

class Book < ActiveRecord::Base
  belongs_to :user
  belongs_to :favorite
end

The idea is that a user can own a book and add a book from another user as favorite. In rails console, i tried User.find(1).favorites.books but got a NoMethodError: undefined method books'. Anduser.books` only returns the books owned by that user

Is there any way to retrieve all books that belong to a user’s favorite in this case?

Answer 1

You are very close, but you shouldn’t have two associations name books. Try something like this:

class User < ActiveRecord::Base
  has_many :books, :dependent => :destroy
  has_many :favorites
  has_many :favorite_books, :through => :favorites, :source => :book
end

Then your query would simply be User.find(1).favorites_books