class BookInstance { BookInstance({ required this.balId, required this.bookId, required this.id, required this.ownerId, required this.price, required this.status, this.soldPrice, }); int balId; int bookId; int id; int ownerId; double price; double? soldPrice; bool status; factory BookInstance.fromJSON(Map json) => BookInstance( balId: json["balId"], bookId: json["bookId"], id: json["id"], ownerId: json["ownerId"], price: json["price"], status: json["status"], ); }