注销时 Angular 将 null 设置为用户对象

Question

我正在尝试在这个 tutorial 之后在 Angular 中构建一个简单的用户身份验证应用程序.当我在用户注销后尝试将 null 设置为 User 对象时遇到错误。

错误:

ERROR in src/app/_services/authentication.service.ts(40,38): error TS2345: Argument of type 'null' is not assignable to parameter of type 'User'.

相关代码(authentication.service.ts):

import {Injectable} from '@angular/core';
import {HttpClient} from '@angular/common/http';
import {BehaviorSubject, Observable} from 'rxjs';
import {map} from 'rxjs/operators';

import {User} from '@/_models';
import { environment } from 'environments/environment';

@Injectable({providedIn: 'root'})
export class AuthenticationService{
    private currentUserSubject: BehaviorSubject<User>;
    public currentUser: Observable<User>;

    constructor(private http: HttpClient){
        this.currentUserSubject = new BehaviorSubject<User>(JSON.parse(localStorage.getItem('currentUser') || '{}'));
        this.currentUser = this.currentUserSubject.asObservable();
    }

    public get currentUserValue(): User{
        return this.currentUserSubject.value;
    }

    login(username: string, password: string){
        return this.http.post<any>(`${environment.apiUrl}/user/login/`, {username, password})
            .pipe(map(user => {
                console.log(user);
                // login successful if there is a jwt token in the response
                if(user.status && user.data.token){
                    // store user details and jwt token in local storage to keep user logged in 
                    // between page refreshes
                    localStorage.setItem('currentUser', JSON.stringify(user));
                    this.currentUserSubject.next(user);
                }
            }));
    }

    logout(){
        // remove user from local storage to log user out
        localStorage.removeItem('currentUser');
        this.currentUserSubject.next(null);
    }
}

我可以通过在 tsconfig.json 中设置 "strict": false 来解决问题，但我想遵循最佳实践。知道为什么会发生这种情况以及如何解决它吗？

更新:用户模型是:

export class User {
    id!: number;
    username!: string;
    token?: string;
}

Answer 1

我刚刚找到了解决方案，以防其他人遇到此问题。我试过了，它在我的应用程序中工作，而且我没有禁用严格检查。

  logout() {
     // remove user from local storage to log user out
     localStorage.removeItem('currentUser');

     // get the user nulled - typescript won't care
     this.currentUserSubject = new BehaviorSubject<User>(JSON.parse(localStorage.getItem('currentUser')!));
     this.currentUser = this.currentUserSubject.asObservable();
   }