flutter 錯誤：需要一個“int”類型的值，但得到一個“Null”類型的值

Question

來自 .NET Core 6 API 的響應正文：

[{"establishmentId":1,"establishmentName":"Secret","addressId":1,"documentationId":1,"address":null,"documentation":null,"associationsEts":[],"prices":[]},{"establishmentId":2,"establishmentName":"HRB","addressId":2,"documentationId":2,"address":null,"documentation":null,"associationsEts":[],"prices":[]}]

我的 model class：

    class Establishment {
      final int id;
      final String name;
      final int addressid;
      final int documentationid;
    
      Establishment(
          {required this.id,
          required this.name,
          required this.addressid,
          required this.documentationid});
    
      factory Establishment.fromJson(Map<String, dynamic> json) {
        return Establishment(
            id: json['id'],
            name: json['name'],
            addressid: json['addressid'],
            documentationid: json['documantationid']);
      }
    }

問題是快照出錯，我希望快照接受 null 值，有人可以幫我解決這個問題嗎？ 謝謝

更新：

json 沒有出現問題，因為我修改了它們，問題仍然存在

class Establishment {
  final int establishmentId;
  final String establishmentName;
  final int addressId;
  final int documentationId;

  Establishment(
      {required this.establishmentId,
      required this.establishmentName,
      required this.addressId,
      required this.documentationId});

  factory Establishment.fromJson(Map<String, dynamic> json) {
    return Establishment(
        establishmentId: json['establishmentId'],
        establishmentName: json['establishmentName'],
        addressId: json['addressId'],
        documentationId: json['documantationId']);
  }
}

Answer 1

您的“fromJson”解析中出現錯誤，將您的工廠 fromJson function 替換為：

factory Establishment.fromJson(Map<String, dynamic> json) {
        return Establishment(
            id: json['establishmentId'],
            name: json['establishmentName'],
            addressid: json['addressId'],
            documentationid: json['documentationId']);
      }

提示：檢查 camelCase 名稱，在您的解析中名稱必須相等。

Answer 2

此代碼仍然無法正常工作“空值而不是 int”

class Establishment {
  final int establishmetnId;
  final String establishmetnName;
  final int addressId;
  final int documentationId;

  Establishment(
      {required this.establishmetnId,
      required this.establishmetnName,
      required this.addressId,
      required this.documentationId});

  factory Establishment.fromJson(Map<String, dynamic> json) {
    return Establishment(
        establishmetnId: json['establishmentId'],
        establishmetnName: json['establishmentName'],
        addressId: json['addressId'],
        documentationId: json['documantationId']);
  }
}

Future<Establishment> fetchEstablishment() async {
  final response =
      await http.get(Uri.parse('https://localhost:7282/api/Establishmens'));
  debugPrint(response.statusCode.toString());
  debugPrint(response.body);
  if (response.statusCode == 200) {
    return Establishment.fromJson(jsonDecode(response.body));
  } else {
    throw Exception('Failed to load Establishments');
  }
}

List<Establishment> parseEstablishment(String responseBody) {
  final parsed = jsonDecode(responseBody).cast<Map<String, dynamic>>();
  return parsed
      .map<Establishment>((json) => Establishment.fromJson(json))
      .toList();
}

Future<List<Establishment>> fetchListEstablishments() async {
  final response =
      await http.get(Uri.parse('https://localhost:7282/api/Establishments'));
  debugPrint(response.statusCode.toString());
  debugPrint(response.body);
  if (response.statusCode == 200) {
    return compute(parseEstablishment,response.body);
  } else {
    throw Exception('Failed to load establishment');
  }
}