currentUser()不能正常工作，为什么我看到该表达式不能求值为函数，因此无法调用它 [英] currentUser() is not working type why I am seeing the expression doesn't evaluate to a function, so it can't be invoked

问题描述

我是Flutter的新手，注册时我正在开发一个简单的身份验证应用程序，我应该导航到聊天屏幕，并且我想抓住当前用户，但是当我调用FireBaseAuth.instance.currentUser()时，我得到了一个例外该表达式不求值一个函数，因此无法调用它."为什么我看到这个?请帮助

I'm new in Flutter, I'm working on a simple authentication app when I registered i should navigate to the chat screen and i want to grab current user but when i call FireBaseAuth.instance.currentUser() I got an exception "the expression doesn't evaluate to a function, so it can't be invoked." Why I'm seeing this? Please Help

import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:flash_chat/constants.dart';

class ChatScreen extends StatefulWidget {
  static const String id = "chatScreen";
  @override
  _ChatScreenState createState() => _ChatScreenState();
}

class _ChatScreenState extends State<ChatScreen> {
  final FirebaseAuth _auth = FirebaseAuth.instance;
  // ignore: deprecated_member_use
  FirebaseUser loginUser;

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

  void getCurrentUser() async {
// HERE I got an Exception "The expression doesn't evaluate to a function, so it can't be invoked."
    final user = await _auth.currentUser();
    if (user != null) {
      loginUser = user;
      print(loginUser.email);
    }
  }

推荐答案

为什么要调用 currentUser 作为函数?这是一个字段，而不是方法.

Why do you invoke currentUser as a function ? It is a field, not a method.

final user = await _auth.currentUser;

更新:由于 currentUser 不会返回将来，因此即使未引起错误(在非未来的对象在封面下导致将对象包裹在新的未来中.

Update: Since currentUser does not return a future, the use of await is useless, even if it doesn't cause errors (await on a non-future object causes, under the cover, the object to be wrapped in a new future).

文档参考: https://pub.dev/documentation/firebase_auth/latest/firebase_auth/FirebaseAuth/currentUser.html

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