Angular Firebase switchmap 和 authstate 代码已弃用

如何解决Angular Firebase switchmap 和 authstate 代码已弃用

我正在学习 Angular，并且正在处理 youtube 上的一些学习视频。下面的代码显示了如何使用 authState。遗憾的是，以下代码已弃用。

@Injectable()
    export class AuthService {

  currentUser: User;

  constructor(private afAuth: AngularFireAuth,private db: AngularFireDatabase) {

              this.afAuth.authState.switchMap(auth => {
                  if (auth) {
                    this.currentUser = new User(auth)
                    return this.db.object(`/users/${auth.uid}`)
                  } else return [];
                })
                .subscribe(user => {
                    this.currentUser['username'] = user.username
                })

             }
 }

我已经更改了一些推荐的部分，这就是我现在得到的：

import { Injectable } from "@angular/core";
import { AngularFireAuth } from "@angular/fire/auth";
import { AngularFirestore } from "@angular/fire/firestore";

import {map,mergeMap,switchMap} from "rxjs/operators";

export class User {

    uid: string;
    username: string = "";
  
    constructor(auth) {
      this.uid = auth.uid
    }
  
  }

    @Injectable()
          export class AuthService {
          
            currentUser: User;
          
            constructor(private afAuth: AngularFireAuth,private db: AngularFirestore) {
          
                        this.afAuth.authState.switchMap(auth => {
                            if (auth) {
                              this.currentUser = new User(auth)
                              return this.db.collection(`/users/${auth.uid}`)
                            } else return [];
                          })
                          .subscribe(user => {
                              this.currentUser['username'] = user.username
                          })
          
                       }
           }

但是我仍然无法使用 switchMap。我从谷歌搜索中尝试了几件事，但我在过时的实现上陷入困境或跌跌撞撞。希望有人能帮忙

我想实现自定义用户名验证。如果您想查看资源，代码取自此视频：https://www.youtube.com/watch?v=NLWHEiH1FZY 可惜是 2017 年的。

编辑：

我已阅读使用 pipe()。我想出了这个代码：

@Injectable()
  export class AuthService {
  
    currentUser: User;
  
    constructor(private afAuth: AngularFireAuth,private db: AngularFirestore) {

                   this user = this.afAuth.authState.pipe(switchMap(auth => {

                        if (auth) {
                            this.currentUser = new User(auth)
                            return this.db.collection(`/users/${auth.uid}`)
                          } else return [];

                    }))

                    .subscribe(user => {
                        this.currentUser['username'] = user.username
                    })
  
               }
   }

在 .switchmap(auth

(parameter) auth: firebase.User
Argument of type '(auth: User) => any[] | AngularFirestoreCollection<unkNown>' is not assignable to parameter of type '(value: User,index: number) => ObservableInput<any>'.
  Type 'any[] | AngularFirestoreCollection<unkNown>' is not assignable to type 'ObservableInput<any>'.
    Type 'AngularFirestoreCollection<unkNown>' is not assignable to type 'ObservableInput<any>'.
      Property '[Symbol.iterator]' is missing in type 'AngularFirestoreCollection<unkNown>' but required in type 'Iterable<any>'.ts(2345)
lib.es2015.iterable.d.ts(51,5): '[Symbol.iterator]' is declared here.