如何在FireStore中获取isAdmin字段并在Flutter中检查它是对还是错

问题描述

大家好，我正在制作一个带有波动的应用程序，对于普通用户管理员和未经身份验证的用户，它们具有不同的视图，但是我要执行的逻辑不起作用，我也不知道为什么.

Hello everyone I'm making an application with flutter which has different views for normal users admins and unauthenticated users, but the logic that I'm going for isn't working and I don't know why.

此处的PS仅是要区分管理员和普通用户.

P.S here I'm only trying to differentiate between admins and normal users.

这就是我想要做的:

Future<bool> isAdmin() async {
    final currentUserUid = _firebaseAuth.currentUser.uid;
    //What I'm trying to do here is get my isAdmin field which is created when a user is created
    final DocumentSnapshot db = await 
          databaseReference.collection('users').doc(currentUserUid).get();
    return db.data().containsKey('isAdmin');
  }

这就是我试图实现的方式

This is how I'm trying to implement it

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

import '../../screens/auth/admin/admin_tab_bar_screen.dart';
import '../../screens/auth/user_tab_bar_screen.dart';
import '../../providers/auth.dart';

class AuthTabBarScreen extends StatelessWidget {
  static const routeName = 'auth-tab-bar-view';
  @override
  Widget build(BuildContext context) {
    final checkUserRole = Provider.of<Auth>(context, listen: false).isAdmin();

    // Here I want to check the Value I'm returning if its true
    if(checkUserRole == true){
      return AdminTabBarScreen();
    } else {
      return UserTabBarScreen();
    }
  }
}

推荐答案

您可以使用 FutureBuilder 来等待将来的构建(在您的情况下为 isAdmin())，然后再进行构建. snapshot.data 是 future 的值.

You can use FutureBuilder which waits for a future (isAdmin() in your case) before building. snapshot.data is the value of the future.

class AuthTabBarScreen extends StatelessWidget {
  static const routeName = 'auth-tab-bar-view';
  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      future: Provider.of<Auth>(context, listen: false).isAdmin(),
      builder: (context, snapshot) => snapshot.hasData
          ? snapshot.data // if isAdmin() is true
              ? AdminTabBarScreen() // return Admin
              : UserTabBarScreen() // else if false, return UserTab
          : Loading(), // while you're waiting for the data, show some kind of loading indicator
    );
  }
}

isAdmin()返回作为未来值的 Future< bool> ，因此当您比较 Future< bool> 和 bool时，您将收到一个相等错误，因为一个是 Future ，另一个是 bool .使用 FutureBuilder()，您的应用将等待 Provider.of< Auth> ... isAdmin()返回值或 snapshot . snapshot 是您未来的异步值，因此调用 snapshot.data 与 await Provider.of< Auth> ... isAdmin()相同.code>，这就是为什么 snapshot.data 返回 bool 而不是 Future< bool> 的原因.了解文档.

isAdmin() returns Future<bool> which is a future value so when you compare Future<bool> and bool, you will receive an equality error because one is a Future and the other is a bool. Using FutureBuilder(), your app waits for Provider.of<Auth>...isAdmin() to return a value or snapshot. A snapshot is an async value of your future so calling snapshot.data is the same as await Provider.of<Auth>...isAdmin() which is why snapshot.data returns a bool and not a Future<bool>. It might be helpful to understand how futures, async, await work documentation.

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