如何在 Flutter 2 中获取 snapshot.error？

Question

我将我的 Flutter 应用程序更新为 Flutter 2，现在当我尝试在我的 StreamBuider 中获取 snapshot.error 时，我得到了这个

这些是带有 Streams 的验证器。

class LoginStreams with Validators {

  dispose() {
    _emailController.close();
    _passwordController.close();
  }

  Function(String) get emailOnChange => _emailController.sink.add;
  Function(String) get passwordOnChange => _passwordController.sink.add;

  final _emailController = StreamController<String>.broadcast();
  final _passwordController = StreamController<String>.broadcast();

  Stream<String> get emailStream => 
    _emailController.stream.transform(emailValidator);
  Stream<String> get passwordStream =>       
 _passwordController.stream.transform(passwordValidator);

}

--

class Validators {
  final passwordValidator = StreamTransformer<String, String>.fromHandlers(
      handleData: (password, sink) {
    password.length >= 5
        ? sink.add(password)
        : sink.addError("La contraseña debe contener más de 5 caracteres");
  });

  final emailValidator =
      StreamTransformer<String, String>.fromHandlers(handleData: (email, sink) {
    if (email.contains('@') && email.contains('.')) {
      sink.add(email);
    } else {
      sink.addError("Ingrese un email válido");
    }
  });
}

StreamBuilder(
            stream: _validators.emailStream,
            builder: (BuildContext context, AsyncSnapshot snapshot)=>TextField(
            keyboardType: TextInputType.emailAddress,
            controller: emailController,
            decoration: InputDecoration(
              errorText: '$snapshot.error',
              labelText: widget.loginModel.emailTextfield,
              border: OutlineInputBorder(
                borderRadius: BorderRadius.circular(CmbSpacing.SpaceMD))),
            onChanged: _validators.emailOnChange,
            ),
          ),
          SizedBox(height: CmbSpacing.SpaceSM),
          StreamBuilder(
            stream: _validators.passwordStream,
            builder: (BuildContext context, AsyncSnapshot snapshot)=>TextField(
            controller: passwordController,
            obscureText: true,
            decoration: InputDecoration(
              errorText: '$snapshot.error',
              suffixIcon: Icon(Icons.visibility_off_outlined),
              labelText: widget.loginModel.passwordTextfield,
                border: OutlineInputBorder(
                borderRadius: BorderRadius.circular(CmbSpacing.SpaceMD))),
            onChanged: _validators.passwordOnChange,
            ),
          ),

如果有人能帮助我，我将不胜感激，我很困惑，因为在升级到 Flutter 2 之后，它曾经工作得很好。

Flutter 2 中的 StreamBuilder 有什么新东西吗？

编辑：

我把“$snapshot.error”改成snapshot.error.toString()

现在我得到了 null。

Answer 1

您没有正确插入错误。如果你想在插值之前调用一个额外的方法，你必须将表达式包装在 ${} 中，例如'${snapshot.error}。在您的情况下，您只是将 .error 附加到 snapshot

的字符串表示形式

替换

errorText: '$snapshot.error'

有

errorText: snapshot.error?.toString()

// or if you want to use it in a sentence
errorText: "This is the error: ${snapshot.error}"

Answer 2

你必须在那边应用条件语句：

errorText: snapshot.hasError ? '${snapshot.error}' : null

我相信这会有所帮助。 :)

如何在 Flutter 2 中获取 snapshot.error？

How to get the snapshot.error in Flutter 2?

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