Moved getting authors from a book to a seperate function

+ Implemented getting quantity in book list

models/author.go

@@ -35,3 +35,18 @@ func GetAuthorByID(id int64) (author Author, exists bool, err error) {
 
 	return author, has, err
 }
+
+// GetAuthorsByBook get all authors of a book
+func GetAuthorsByBook(bookID int64) (authors []Author, err error) {
+	err = x.
+		Table("authors_books").
+		Join("INNER", "authors", "authors_books.author_id = authors.id").
+		Where("book_id = ?", bookID).
+		Find(&authors)
+
+	if err != nil {
+		return authors, err
+	}
+
+	return authors, err
+}

models/book.go

@@ -74,27 +74,16 @@ func GetBookByID(ID int64) (book Book, exists bool, err error) {
 		}
 
 		// Get publisher. We can't join it because xorm ignores the PublisherID option in struct
-		publisher := Publisher{ID: book.Publisher}
-		_, err = x.Get(&publisher)
+		book.PublisherFull, _, err = GetPublisherByID(book.Publisher)
 		if err != nil {
 			fmt.Println("Error getting publisher:", err)
 		}
-		book.PublisherFull = publisher
 
 		// Get all authors
-		var authors []Author
-		err = x.
-			Table("authors_books").
-			Select("authors.*").
-			Join("INNER", "authors", "authors_books.author_id = authors.id").
-			Where("book_id = ?", book.ID).
-			Find(&authors)
-
+		book.Authors, err = GetAuthorsByBook(book.ID)
 		if err != nil {
 			fmt.Println("Error getting authors:", err)
 		}
-
-		book.Authors = authors
 	}
 
 	return book, has, err

models/books_list.go

@@ -25,30 +25,26 @@ func ListBooks(searchterm string) (books []*Book, err error) {
 		}
 	}
 
-	// Get all authors and publishers
+	// Get all authors, publishers and quantities
 	for i, book := range books {
 
+		// Get quantities
+		books[i].Quantity, err = GetQuantityByBook(book.ID)
+		if err != nil {
+			fmt.Println("Error getting quantity:", err)
+		}
+
 		// Get publisher
-		publisher := Publisher{ID: book.Publisher}
-		_, err := x.Get(&publisher)
+		books[i].PublisherFull, _, err = GetPublisherByID(book.Publisher)
 		if err != nil {
 			fmt.Println("Error getting publisher:", err)
 		}
-		books[i].PublisherFull = publisher
 
 		// Get all authors
-		var authors []Author
-		err = x.
-			Table("authors_books").
-			Join("INNER", "authors", "authors_books.author_id = authors.id").
-			Where("book_id = ?", book.ID).
-			Find(&authors)
-
+		books[i].Authors, err = GetAuthorsByBook(book.ID)
 		if err != nil {
 			fmt.Println("Error getting authors:", err)
 		}
-
-		books[i].Authors = authors
 	}
 
 	return books, err