How to fix error: "Null check operator used on a null value"?

Question

I'm getting a Null check operator used on a null value error in flutter.

Map<String, dynamic> newUserMap = jsonDecode(authenticate.body);
print('newUserMap?');
var authNodeUser = TokenContent.fromJson(newUserMap);
print('authNodeUser?');
String? jwtToken = authNodeUser.jwtToken;
print('jwtToken = ' + authNodeUser.jwtToken!);

as I'm seeing newUserMap? and authNodeUser? I'm guessing the error occurs here;

String? jwtToken = authNodeUser.jwtToken;
print('jwtToken = ' + authNodeUser.jwtToken!);

Here's the TokenContent class;

class TokenContent {
  int? currUser;
  String? jwtToken;
  String? refreshToken;

  TokenContent({this.currUser, this.jwtToken, this.refreshToken});

  TokenContent.fromJson(Map<String, dynamic> json) {
    currUser = json['currUser'];
    jwtToken = json['token'];
    refreshToken = json['refreshToken'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['currUser'] = this.currUser;
    data['jwtToken'] = this.jwtToken;
    data['refreshToken'] = this.refreshToken;
    return data;
  }
}

How can I fix this?

Answer 1

Print newUserMap and make sure jwtToken exist in the http response.