如何在Flutter中将api中的0或null值设置为Model类

Question

我正在调用一个具有混合值的api。一些值返回0，另一些返回int。但当我调用该api时，我会得到以下错误：

The getter 'actualTotalFee' was called on null.
Receiver: null
Tried calling: actualTotalFee

我的api响应是：

"summary": {
"said_fee": 0,
"nos": 11,
"currentPayable": 0,
"eximp-sem": 1,
"sum_of_tution_fee": 173875,
"common_scholarship": 0,
"actual_total_fee": 0,
"special_scholarship": 10000,
"per_semester_fee": 0,
"per_semester_fee_without_scholarship": 0,
"total_paid": 190000,
"total_current_due": -200000,
"Due_Up_to_April": -200000,
"total_due": -200000
}

我的api调用方法：

// Getting Accounts Summery
Future<AccountSummery> fetchAccountSummery(int userId) async {

final url =
Api.baseUrl + 'student_account_info_summary/$userId?token=$authToken';
try {
final response = await get(Uri.encodeFull(url));
final loadedItem = json.decode(response.body);
if (response.statusCode == 200) {
return AccountSummery.fromJson(loadedItem['summary']);
} else {
throw Exception('Error in getting account summery');
}
} catch (error) {
throw error;
}
}

我的模型调用：

class AccountSummery {
final int actualTotalFee;
final int specialScholarship;
final int perSemesterWithoutScholarship;
final int perSemesterFee;
final int totalPaid;
final double totalCurrentDue;
final int totalDue;
AccountSummery(
{
this.actualTotalFee,
this.specialScholarship,
this.perSemesterWithoutScholarship,
this.perSemesterFee,
this.totalPaid,
this.totalCurrentDue,
this.totalDue
});
factory AccountSummery.fromJson(Map<String, dynamic> json) {
return AccountSummery(
actualTotalFee: json['actual_total_fee'],
specialScholarship: json['special_scholarship'],
perSemesterWithoutScholarship: json['per_semester_fee_without_scholarship'],
perSemesterFee: json['per_semester_fee'],
totalPaid: json['total_paid'],
totalCurrentDue: json['total_current_due'],
totalDue: json['total_due'],
);
}
}

因为一些回应，比如"；actual_total_ feee"per_semester_fee"；etc返回0值，我的api响应方法失败。

有什么方法可以运行api方法或为我的模型类设置0值吗？

Answer 1

在您的模型中

actualTotalFee: json['actual_total_fee'] ?? 0,

在您的呼叫

AccountSummeryObj?.actualTotalFee ?? 0

Answer 2

您可以通过两种方式实现：

1. actualTotalFee: json['actual_total_fee'] ?? 0

2. actualTotalFee: json['actual_total_fee'] !=null ? json['actual_total_fee'] : 0

Answer 3

如果API为空，则使用此选项将默认值设置为0：

actualTotalFee: json['actual_total_fee'] ?? 0,