angular - RxJS - 返回具有值(value)的主题

Question

我创建了一个身份验证服务，组件可以订阅权限更改(登录/注销/Angular 色更改等)。 在 isAuthenticated 函数中，我返回一个主题。 问题是我想用一个值返回主题(比如 Observable.of。现在，我正在使用 setTimeout。

@Injectable()
export class AuthenticationService {
  constructor(private credentials: CredantialsStorageService,
    private oauthService:OAuth2Service,
    private secureHttp: SecureHttpService) {}
  
  private isAuthenticatedSubject: Subject<boolean> = new Subject<boolean>();

  login(email:string, password: string, remember?:boolean ): Observable<boolean> {
      return this.oauthService.login(email, password)
        .flatMap(() => this.getAndStoreUserCredantials())
        .map((userCredantials: any) =>  {
          this.isAuthenticatedSubject.next(true);
          return true;
        })
 
  }

  logout(): Observable<void> {
    return this.secureHttp.post('/logout', null)
      .finally(() => {
        this.credentials.clear();
        this.oauthService.clear();
        this.isAuthenticatedSubject.next(false);
      })
      .map(() =>  null);
  }

  isAuthenticated(): Observable<boolean> {
    setTimeout(() => { //Hack - find a way to change this
      this.isAuthenticatedSubject.next(this.oauthService.isAuthenticated());
    })
    return this.isAuthenticatedSubject;
  }

  private getAndStoreUserCredantials() {
    return this.secureHttp.get('/user/info')
      .map((res:Response) => {
        let userCredantials = res.json();
        this.credentials.set(userCredantials);
        return userCredantials;
      })
  }
}

Answer 1

我认为最简单的方法是使用 startWith() 运算符:

isAuthenticated(): Observable<boolean> {
    return this.isAuthenticatedSubject.startWith(this.oauthService.isAuthenticated());
}

您也可以使用 BehaviorSubject 或 ReplaySubject 但它们只会重复已经通过它们的值。也许还可以查看此答案以获取更详细的描述有什么区别:Does startWith() operator turns Observable into ReplaySubject(1)? .