Flutter Unhandled Exception: type 'Null' is not a subtype of type 'String'-CodePudding

I'm registering a user but when I fill form I get error

Unhandled Exception: type 'Null' is not a subtype of type 'String'

Error I'm getting on this line

authRepo.saveUserToken(response.body["token"]);

Here is registration method from

auth_controller.dart

Future<ResponseModel> registration(SignUpBody signUpBody) async {
    _isLoading = true;
    update();
    Response response = await authRepo.registration(signUpBody);
    late ResponseModel responseModel;
    if (response.statusCode == 200) {
      authRepo.saveUserToken(response.body["token"]);
      responseModel =
          ResponseModel(success: true, enMessage: response.body['token']);
      // responseModel = ResponseModel(true, response.body["token"]);
    } else {
      responseModel =
          ResponseModel(success: false, enMessage: response.statusText);
      // responseModel = ResponseModel(false, response.statusText!);
    }
    _isLoading = false;
    update();
    return responseModel;
  }

saveUserToken

 Future<bool> saveUserToken(String token) async {
    apiClient.token = token;
    apiClient.updateHeader(token);
    return await sharedPreferences.setString(AppConstants.TOKEN, token);
  }

CodePudding user response：

Without seeing your saveUserToken is difficult to say, but it seems that response.body["token"] is null and since saveUserToken will be something like saveUserToken(String token) { ... }, Dart is raising a type error.

I suggest you to check if your token is null or not and then throwing manually if it is. Something like this:

Future < ResponseModel > registration(SignUpBody signUpBody) async {
    _isLoading = true;
    update();

    try {
        Response response = await authRepo.registration(signUpBody);
        late ResponseModel responseModel;
        final String token = response.body["token"];

        if (response.statusCode == 200 && token != null) {
            authRepo.saveUserToken();
            responseModel = ResponseModel(success: true, enMessage: response.body['token']);
        } else {
           throw new Error('A custom message');
        }
    } on Error catch (e) {
        print(e);
        responseModel = ResponseModel(success: false, enMessage: response.statusText);
    } finally {
        _isLoading = false;
        update();
    }

    return responseModel;
}

CodePudding user response：

Check if response.body["token"] is really not null. You can output the variable via console. Otherwise send the whole error message. It is certainly not only one single line long.

CodePudding user response：

if(response.body["token"]) // do things

wouldn't this work?