class BookInstance {
  BookInstance({
    required this.balId,
    required this.bookId,
    required this.id,
    required this.ownerId,
    required this.price,
    required this.available,
    this.soldPrice,
  });

  int balId;
  int bookId;
  int id;
  int ownerId;
  double price;
  double? soldPrice;
  bool available;

  factory BookInstance.fromJSON(Map<String, dynamic> json) => BookInstance(
    balId: json["bal_id"],
    bookId: json["book_id"],
    id: json["id"],
    ownerId: json["owner_id"],
    price: json["price"],
    available: json["available"],
    soldPrice: json["sold_price"] ?? 0,
  );
}