How to use the withCriteria results in a new withCriteria query in Grails?

Question

Consider the first query:

def books =  Book.withCriteria {
   eq("category", "fiction")
}

How can I use the result of this query in the next query to get all the authors who wrote these books?

I tried:

def authors = Author.withCriteria {
  'in'("books", books)
}

but this is not working. What can I do to fix it?

Answer 1

Can't you just query the association directly?

def authors = Author.withCriteria {
  books {
    eq("category", "fiction")
  }
}