dart - 如何从JSON创建上级和子类？

Question

我一直在尝试找出如何使用命名构造函数从JSON构造父类和子类。以下是我的示例，并提供了一些关于fromJson方法主体中尝试过的内容的注释。谁能指出我正确的方向？谢谢!

class Item {
  final String name;
  final int id;
  final String image;
  final double price;
  final bool available;

  Item(this.name, this.id, this.image, this.price, this.available);

  Item.fromJson(Map<String, dynamic> json)
      : name = json['name'],
        id = json['id'],
        image = json['image'],
        price = json['price'],
        available = json['available'];

}

class CartItem extends Item {
  final int quantity;

  CartItem({
    @required this.quantity,
    @required name,
    @required id,
    @required price,
    @required image,
    @required available

  }): super(id, name, image, price, available)
  
  CartItem.fromJson(Map<String, dynamic> json) 
    : quantity = json['quantity'],
    // for whatever ever reason, super here seems to refer to CartItem
    // so this doesn't work
    super.name = json['name'],
    // calling 'name' without the super doesn't work either
    name = json['name']
}

Answer 1

您应该在子类的super构造函数中使用fromJson的fromJson构造函数。您可以将子级中的Map直接传递给super，而不会出现问题。例如:

CartItem.fromJson(Map<String, dynamic> json) 
    : quantity = json['quantity'],
    super.fromJson(json);