Rails Unique names in the scope of a parent

Question

Suppose I have:

class Author    
  has_many :books

class Book
  belongs_to :author
  validates :name, :presence => true, :uniqueness => true 

I want to change this so that the name of the book is only unique within the scope of the author, i.e. no author has two books with the same name, but two authors could have a book with the same name. Is this possible?

Answer 1

It's very possible and quite easy:

validates :name, :presence => true, :uniqueness => {scope: :author}