I have two classes, library and book. library has_many :books.
When I want to add a book to a library, I call library.books << book. So
far so good.
However, before I add the book, I need to check whether it’s already in
the library. I thought I would do this by adding ‘unless
library.books.find(book)’, but this doesn’t work because if find()
doesn’t find anything it seems to throw an exception rather than
Can anyone tell me how I can check whether the book is already in the