Question

我是angular和firebase的新手。当我尝试从of导入rxjs时，也尝试使用switchMap返回null时，出现此错误。 auth.service.ts

import { ActivatedRoute } from '@angular/router'
import { Observable,  of } from 'rxjs';
import { Injectable } from '@angular/core';
import { AppUser } from './models/app-user'
import { AngularFireAuth } from '@angular/fire/auth';
import { switchMap } from 'rxjs/operators';
import * as firebase from 'firebase';
import { UserService } from './user.service';

@Injectable({
  providedIn: 'root'
})
export class AuthService {
  user$: Observable<firebase.User>;

  constructor(
    private userService: UserService,
    private afAuth: AngularFireAuth,  
    private route: ActivatedRoute) { 
    this.user$=afAuth.authState;
  }

  login(){
    let returnUrl=this.route.snapshot.queryParamMap.get('returnUrl')||'/'
    localStorage.setItem('returnUrl',returnUrl)
    this.afAuth.auth.signInWithRedirect(new firebase.auth.GoogleAuthProvider())
  }
  logout(){
    this.afAuth.auth.signOut()
  }

  get appUser$():Observable<AppUser>{
    return this.user$
    .pipe(switchMap(user=> {
      if(user) return this.userService.get(user.uid).valueChanges();
    return Observable.of(null);    <==line of error
    })
}
}

user.service.ts

import { Injectable } from '@angular/core';
import { AngularFireDatabase, AngularFireObject } from '@angular/fire/database';
import * as firebase from 'firebase';
import { AppUser } from './models/app-user';

@Injectable({
  providedIn: 'root'
})
export class UserService {

  constructor(private db:AngularFireDatabase) { }

  save(user: firebase.User){
    this.db.object('/users/'+user.uid).update({
      name: user.displayName,
      email: user.email
    })
  }

  get(uid: string):AngularFireObject<AppUser>{
    return this.db.object('/users/'+uid)
  }
}

app.user.ts

export interface AppUser{
    name: string,
    email:string,
    isAdmin: boolean
}

获取Type 'Observable<unknown>' is not assignable to type 'Observable<AppUser>'作为错误消息。

Answer 1

尝试使用typescript optional parameters

代替name: string;

更改为name?: string;

export class AppUser {
  name?: string;
  email?: string;
  isAdmin?: boolean;
  photoURL?: string;
}

希望如此。

Answer 2

您似乎已经在strictNullChecks中启用了tsconfig.json，因此不允许您分配null来键入AppUser，这是正确的。

因此，您可以将返回类型定义为Observable<AppUser | null>，其中还包括null值。

也许还可以尝试将RxJS升级到可能的最新版本。我认为of的键入https://github.com/ReactiveX/rxjs/issues/4723曾经存在问题，但这可能与您的问题无关。

Answer 3

感谢您的回复。通过向isAdmin?: string和app-user.ts中添加import { of } from 'rxjs' ... return of(null) 工作。

Answer 4

我遇到了同样的问题，我所做的只是添加<?php // YOUR SQL CONNECT GOES HERE. // REPLACE $data with PDO/MYSQLI QUERY DATA. $data = [ [ ( Object )["axis" => "Battery Life","value" => (rand(1, 99))], ( Object )["axis" => "Brand","value" => rand(1, 99)], ( Object )["axis" => "Contract Cost","value" => rand(1, 99)], ( Object )["axis" => "Design And Quality","value" => rand(1, 99)], ( Object )["axis" => "Have Internet Connectivity","value" => rand(1, 99)], ( Object )["axis" => "Price Of Device","value" => rand(1, 99)], ( Object )["axis" => "To Be A Smartphone","value" => rand(1, 99)], ] ]; echo json_encode($data);

类型'Observable <未知>'不可分配给类型'Observable <Something>'

4 个答案: