使用 Flutter app + Deno + MongoDB 后端的奇怪错误

Question

我想写一个简单的注册函数，这是我的代码：

auth_screen.dart:

  Future<void> _submit() async {
    if (!_formKey.currentState!.validate()) {
      // Invalid!
      return;
    }
    _formKey.currentState!.save();
    setState(() {
      _isLoading = true;
    });
    try {
      if (_authMode == AuthMode.Login) {
        // Log user in
        await Provider.of<Auth>(context, listen: false).login(
          _authData['email'] as String,
          _authData['password'] as String,
        );
      } else {
        // Sign user up
        await Provider.of<Auth>(context, listen: false).signup(
          _authData['email'] as String,
          _authData['password'] as String,
          
        );
      }
    } on HttpException catch (error) {
      var errorMessage = 'Authentication failed';
      print("this is the auth data");
      print(_authData);
      if (error.toString().contains('EMAIL_EXISTS')) {
        errorMessage = 'This email address is already in use.';
      } else if (error.toString().contains('INVALID_EMAIL')) {
        errorMessage = 'This is not a valid email address';
      } else if (error.toString().contains('WEAK_PASSWORD')) {
        errorMessage = 'This password is too weak.';
      } else if (error.toString().contains('EMAIL_NOT_FOUND')) {
        errorMessage = 'Could not find a user with that email.';
      } else if (error.toString().contains('INVALID_PASSWORD')) {
        errorMessage = 'Invalid password.';
      }
      _showErrorDialog(errorMessage);
    } catch (error) {
      var errorMessage = 'Could not authenticate you. Please try again later.' +
          error.toString();
      _showErrorDialog(errorMessage);
    }

    setState(() {
      _isLoading = false;
    });
  }

auth.dart:


  Future<void> signup(String email, String password) async {
    return _authenticate(email, password, 'register');
  }

  Future<void> _authenticate(
      String email, String password, String urlSegment) async {

    final url = Uri.parse('http://10.0.2.2:8000/api/$urlSegment');
    // final url = Uri.http('http://localhost:8000/api/', 'urlSegment');
    try {
      final response = await http.post(
        url,
        body: json.encode(
          {
            'email': email,
            'password': password,

            //'returnSecureToken': true,
          },
        ),
      );
      final responseData = json.decode(response.body);
      if (responseData['error'] != null) {
        throw HttpException(responseData['error']['message']);
      }
      _token = responseData['idToken'];
      _userId = responseData['localId'];
      _expiryDate = DateTime.now().add(
        Duration(
          seconds: int.parse(
            responseData['expiresIn'],
          ),
        ),
      );
      _autoLogout();
      notifyListeners();
      final prefs = await SharedPreferences.getInstance();
      final userData = json.encode(
        {
          'token': _token,
          'userId': _userId,
          'expiryDate': _expiryDate!.toIso8601String(),
        },
      );
      prefs.setString('userData', userData);
    } catch (error) {
      throw error;
    }
  }

这是项目的后端（Deno）部分：

auth_controller.ts:

async register(ctx: RouterContext) {
    const { email, password } = await ctx.request.body().value;
    let user = await User.findOne({ email });
    if (user) {
        ctx.response.status = 422;
        ctx.response.body = { message: "Email is already exist" };
        return;
    }
    const hashedPassword = hashSync(password);
    user = new User({ email, password: hashedPassword });
    await user.save();
    ctx.response.status = 201;
    ctx.response.body = {
        id: user.id,
        name: user.name,
        email: user.email
    };
}

这是 user.ts class:


export default class User extends BaseModel {
    public id: string = "";
    public name: string = "";
    public email: string = "";
    public password: string = "";
    constructor({ id = "", name = "", email = "", password = "" }) {
        super();
        this.id = id;
        this.name = name;
        this.email = email;
        this.password = password;
    }
    static async findOne(params: object): Promise<User | null> {
        const user = await userCollection.findOne(params);
        if (!user) {
            return null;
        }
        return new User(User.prepare(user));
    }
    async save() {
        const _id = await userCollection.insertOne(this);
        this.id = _id;
        return this;
    }
}

当我想在 Android 模拟器上测试应用程序时收到此错误消息：

type 'Null' is not a subtype of type 'String'

当我使用 Postman 尝试后端服务器并将 post 请求发送到 http://0.0.0.0:8000/api/register 地址时。我得到了正确的响应并且它有效，但我不知道为什么我使用 Flutter 应用程序得到 Null 响应？

我尝试在应用程序的前端和后端打印变量，看起来它们都很好而且正确，但我不明白为什么会收到此错误消息？！

Answer 1

您收到的响应值似乎是 null 而不是 String。

编辑：

 Future<void> signup(String email, String password) async {
    return _authenticate(email, password, 'register');
  }

检查 email 和 password 不是 null。并获得正确的值。

Answer 2

可能你在这部分的地图中得到了一个空值，因为地图return当找不到键时是一个空值，检查地图值是否不为空

    try {
      if (_authMode == AuthMode.Login) {
        // Log user in
        await Provider.of<Auth>(context, listen: false).login(
          _authData['email'] as String,  // can return a null value
          _authData['password'] as String,   // can return a null value
        );
      } else {
        // Sign user up
        await Provider.of<Auth>(context, listen: false).signup(
          _authData['email'] as String,   // can return a null value
          _authData['password'] as String,   // can return a null value
          
        );
      }
    }

Answer 3

其实问题出在这两行代码：

_token = responseData['idToken']; _userId = responseData['localId'];

因为它没有传递这些数据作为后端的响应。

使用 Flutter app + Deno + MongoDB 后端的奇怪错误

Strange error using Flutter app + Deno + MongoDB backend

mongodb

flutter

undefined

typeerror

deno