Json 可序列化 - 参数无效(输入):不得为 null

Question

我正在尝试在我的模型类中设置 JSON 值。但它返回的错误为无效参数(输入(：不得为空

用户帐户.dart

import 'package:json_annotation/json_annotation.dart';
part 'userAccount.g.dart';

@JsonSerializable(nullable: true,disallowUnrecognizedKeys:true,includeIfNull:true)
class UserAccount{
String id;
String name;
String email;
String profile_pic;
String country;
String phoneNumber;
bool isNewUser;
int role;
int account_status;
String token;
DateTime token_expiry;
String facebook_profile_url;
String google_profile_url;
String twitter_profile_url;
int matchStixx_count;
DateTime created_at;
DateTime updated_at;

UserAccount({
this.id,
this.name,
this.email,
this.profile_pic,
this.country,
this.phoneNumber,
this.isNewUser,
this.role,
this.account_status,
this.token,
this.token_expiry,
this.facebook_profile_url,
this.google_profile_url,
this.twitter_profile_url,
this.matchStixx_count,
this.created_at,
this.updated_at
});
factory UserAccount.fromJson(Map<String,dynamic> json) => _$UserAccountFromJson(json);
Map<String,dynamic> toJson() =>_$UserAccountToJson(this);
}

UserAccount.g.dart

part of 'userAccount.dart';
UserAccount _$UserAccountFromJson(Map<String, dynamic> json) {
return UserAccount(
id: json['_id'] as String,
name: json['name'] as String,
email: json['email'] as String,
profile_pic: json['profile_pic'] as String,
country: json['country'] as String,
phoneNumber: json['phoneNumber'] as String,
isNewUser: json['isNewUser'] as bool,
role: json['role'] as int,
account_status: json['account_status'] as int,
token: json['token'] as String,
token_expiry: DateTime.parse(json['token_expiry'] as String),
facebook_profile_url: json['facebook_profile_url'] as String,
google_profile_url: json['google_profile_url'] as String,
twitter_profile_url: json['twitter_profile_url'] as String,
matchStixx_count: json['matchStixx_count'] as int,
created_at: DateTime.parse(json['created_at'] as String),
updated_at: DateTime.parse(json['updated_at'] as String)
);
}
Map<String, dynamic> _$UserAccountToJson(UserAccount instance) =>
<String, dynamic>{
'id': instance.id,
'name': instance.name,
'email': instance.email,
'profile_pic': instance.profile_pic,
'country': instance.country,
'phoneNumber': instance.phoneNumber,
'isNewUser': instance.isNewUser,
'role': instance.role,
'account_status': instance.account_status,
'token': instance.token,
'token_expiry': instance.token_expiry,
'facebook_profile_url': instance.facebook_profile_url,
'google_profile_url': instance.google_profile_url,
'twitter_profile_url': instance.twitter_profile_url,
'matchStixx_count': instance.matchStixx_count,
'created_at': instance.created_at,
'updated_at': instance.updated_at,
};

JSON数据- 此 JSON 存储在 (responseBody["userData"](

{_id： 1， 姓名：某名， 电子邮件： [e-mail]， profile_pic： https://xyz/yzz.png， isNewUser： true， role： 1， account_status： 1， matchStixx_count：20，created_at：2020-05-15T06：41：24.528Z，__v：0}

模型初始化

userAccount = new UserAccount.fromJson(responseBody["userData"]); //geting error here

Answer 1

如果您发布完整的堆栈跟踪，它会容易得多，因为它包含有关哪些字段为 null 的信息：

Unhandled exception:
Invalid argument(s) (input): Must not be null
#0      _RegExp.firstMatch (dart:core-patch/regexp_patch.dart:222:24)
#1      DateTime.parse (dart:core/date_time.dart:282:22)
#2      _$UserAccountFromJson (file:///stackoverflow.dart:64:30)
#3      new UserAccount.fromJson (file:///stackoverflow.dart:47:7)
#4      main (file:///stackoverflow.dart:5:15)
#5      _startIsolate.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:301:19)
#6      _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)

代码中有问题的行如下：

token_expiry: DateTime.parse(json['token_expiry'] as String),

由于您的 json 不包含token_expiry因此此处的结果将为 null。但是由于DateTime.parse不接受null作为输入，因此会出现错误"不得为null"。

对于修复，您可以将该行更改为如下所示：

token_expiry: json['token_expiry'] == null ? null : DateTime.parse(json['token_expiry'] as String),

然后，这将为字段updated_at给出相同的错误，因此您也应该正确执行：

created_at: json['created_at'] == null ? null : DateTime.parse(json['created_at'] as String),
updated_at: json['updated_at'] == null ? null : DateTime.parse(json['updated_at'] as String));

Answer 2

如果有人路过并遇到同样的问题，您需要验证您的变量名称，就像您有Map<String, dynamic>一样，那么您需要验证键名称，这就是发生在我身上的事情 希望这有助于好运