Null safety implementation of AtClientService Wrapper.

AtClientService.dart

import 'package:at_client_mobile/at_client_mobile.dart';
import 'package:at_client/at_client.dart';
import 'package:at_commons/at_commons.dart';

import 'package:path_provider/path_provider.dart';
import 'package:at_birdhouse/utils/constants.dart';//TODO YOUR constants file here

class ClientService {
  ClientService._internal();
  static final ClientService _singleton = ClientService._internal();
  factory ClientService.getInstance() => _singleton;

  Map<String?, AtClientService> _atClientServiceMap = {};
  String? path;

  //* Post onboard variables
  String? _atsign;
  AtClientService? _atClientServiceInstance;
  AtClientImpl? _atClientInstance;

  //* AtClientService Getters
  AtClientService _getAtClientServiceForAtSign({String? atsign}) =>
      _atClientServiceInstance ??=
          _atClientServiceMap[atsign] ?? AtClientService();

  AtClientImpl _getAtClientForAtsign({String? atsign}) => _atClientInstance ??=
      _getAtClientServiceForAtSign(atsign: atsign).atClient!;

  //* Onboarding process
  Future<AtClientPreference> getAtClientPreference({String? cramSecret}) async {
    path ??= (await getApplicationSupportDirectory()).path;
    return AtClientPreference()
      ..isLocalStoreRequired = true
      ..commitLogPath = path
      ..cramSecret = cramSecret
      ..namespace = AtConstants.NAMESPACE
      ..syncStrategy = SyncStrategy.IMMEDIATE
      ..rootDomain = AtConstants.ROOT_DOMAIN
      ..rootPort = AtConstants.ROOT_PORT
      ..hiveStoragePath = path;
  }

  void postOnboard(Map<String?, AtClientService> value, String? atsign) {
    _atClientServiceMap = value;
    _atsign = atsign;
    _getAtClientForAtsign(atsign: _atsign);
    sync();
  }

  //* GETTERS (should only be called after onboarding)
  String get atsign => _atsign!;
  AtClientService get atClientServiceInstance => _atClientServiceInstance!;
  AtClientImpl get atClientInstance => _atClientInstance!;

  //* VERBS
  Future<void> sync() async {
    await _getAtClientForAtsign().getSyncManager()!.sync();
  }

  Future<String> get(AtKey atKey) async =>
      (await _getAtClientForAtsign().get(atKey)).value;

  Future<bool> put(AtKey atKey, String value) async =>
      await _getAtClientForAtsign().put(atKey, value);

  Future<bool?> delete(AtKey atKey) async =>
      await _getAtClientForAtsign().delete(atKey);

  Future<List<AtKey>> getAtKeys({String? regex, String? sharedBy}) async {
    regex ??= AtConstants.NAMESPACE_REGEX;
    return await _getAtClientForAtsign()
        .getAtKeys(regex: regex, sharedBy: sharedBy);
  }

  Future<bool> notify(
      AtKey atKey, String value, OperationEnum operation) async {
    return await _getAtClientForAtsign().notify(atKey, value, operation);
  }
}

OnboardingScreen.dart

class OnboardingScreen extends StatefulWidget {
  OnboardingScreen({Key key}) : super(key: key);
  static final id = "onboarding_screen";
  @override
  _OnboardingScreenState createState() => _OnboardingScreenState();
}

class _OnboardingScreenState extends State<OnboardingScreen> {
  String atSign;
  ClientService clientService = ClientService.getInstance();
  var atClientPreference;
  var _logger = AtSignLogger('@birdhouse');

  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        resizeToAvoidBottomInset: false,
        appBar: AppBar(
          backgroundColor: AppColors.BLUE,
          title: Text('Home'),
        ),
        // appBar: AppBar(
        //   title: const Text('Plugin example app'),
        // ),
        body: Builder(
          builder: (context) => Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Center(
                child: TextButton(
                    onPressed: () async {
                      atClientPreference =
                          await clientService.getAtClientPreference();
                      Onboarding(
                        appAPIKey: AtConstants.APP_API_KEY,
                        context: context,
                        atClientPreference: atClientPreference,
                        domain: AtConstants.ROOT_DOMAIN,
                        appColor: AppColors.BLUE,
                        onboard: clientService.postOnboard,
                        onError: (error) {
                          _logger.severe('Onboarding throws $error error');
                        },
                        nextScreen: BasketScreen(),
                      );
                    },
                    child: Text("Let's Go!")),
              ),
              SizedBox(
                height: 10,
              ),
              TextButton(
                  onPressed: () async {
                    KeyChainManager _keyChainManager =
                        KeyChainManager.getInstance();
                    var _atSignsList =
                        await _keyChainManager.getAtSignListFromKeychain();
                    _atSignsList?.forEach((element) {
                      _keyChainManager.deleteAtSignFromKeychain(element);
                    });
                    ScaffoldMessenger.of(context).showSnackBar(SnackBar(
                        content: Text(
                      'Keychain cleaned',
                      textAlign: TextAlign.center,
                    )));
                  },
                  child: Text(
                    "Reset Keychain",
                    style: TextStyle(color: Colors.blueGrey),
                  ))
            ],
          ),
        ),
      ),
    );
  }
}