StreamProvider 和 Firebase

Question

void main() async {
  ...
  final AuthenticationProvider authenticationProvider = AuthenticationProvider();
  await authenticationProvider.initialize();
  runApp(
    MultiProvider(
      providers: [
        Provider<AuthenticationProvider>(create: (_) => authenticationProvider),
        StreamProvider<UserModel>(
          create: (_) => authenticationProvider.currentUser,
          initialData: UserModel(
            id: '',
            email: '',
            displayName: '',
            photo: null,
            premium: false,
            travels: [],
          ),
        )
      ],
      child: MiRoulotte(),
    ),
  );
}

我创建了一个提供程序，它使用当前用户数据生成一个流，当用户退出或登录时，这些数据会发生变化，但数据不会改变。当我退出时，流应该为空，然后当我登录时，流应该是用户数据。

class AuthenticationProvider {
  Stream<UserModel>? _currentUser;
  Stream<UserModel>? get currentUser => this._currentUser;

  initialize() async {
    ...
    this._currentUser = FirebaseFirestore.instance
      .collection('users')
      .doc(FirebaseAuth.instance.currentUser?.uid)
      .snapshots()
      .map((user) => UserModel.fromJson(user.data() as Map<String, dynamic>));
    ...
  }

  Future signIn({required String email, required String password}) async {
    ...
    this._currentUser = FirebaseFirestore.instance
      .collection('users')
      .doc(userCredential.user?.uid)
      .snapshots()
      .map((user) => UserModel.fromJson(user.data() as Map<String, dynamic>));
    ...
  }


  Future signOut() async {
    ...
    this._currentUser = null;
    ...
  }
}

Answer 1

您实际上并不希望您的Stream 成为null，而是让它发出一个null 值。 AuthenticationProvider 可以有一个 StreamController，您可以使用它将当前用户对象的新值添加到流中。

class AuthenticationProvider {
  final StreamController _controller = SteamController<UserModel?>();
  Stream<UserModel?> get userStream => _controller.stream;

  Future<void> initialize() async {
    final user = // get usermodel from firebase
    _controller.add(user);
  }

  Future<void> signIn({required String email, required String password}) async {
    ...
    final user = // get usermodel from firebase
    _controller.add(user);
  }

  void signOut() {
    _controller.add(null);
  }
}

别忘了在 dispose 时关闭StreamController：

// in main
Provider<AuthenticationProvider>(
  create: (_) => authenticationProvider,
  dispose: (provider) => provider.dispose(),
),

// in AuthenticationProvider
void dispose() {
  _controller.close();
}