Angular 4 DI：等待方法完成

Question

为了避免循环依赖，我使用Injector来注入AuthService，但是当我运行应用程序Angular时，在设置intercept()属性之前执行authService方法！ ！

@Injectable()
export class TokenInterceptorService implements HttpInterceptor{
  private authService;
   constructor(private injector: Injector) {
      setTimeout(() => {
          this.authService = injector.get(AuthService);
console.log('===========================================',this.authService);
        });
      }

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        request = request.clone({
          setHeaders: {
            Authorization: `Bearer ${this.authService.getToken()}`
          }
        });

        return next.handle(request);
      }
    }

Answer 1

setTimeout不应该被用来避免循环依赖，因为它会导致像这样的竞争条件。

避免循环依赖的正确方法是就地检索它们。在拦截器类的情况下，它是intercept方法：

export class TokenInterceptorService implements HttpInterceptor {
  constructor(private injector: Injector) {}

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const authService = this.injector.get(AuthService);
    ...
  }
}

如果在由导致循环依赖的服务（AuthService）执行的请求中有可能使用拦截器，则应该在拦截器中添加额外的安全措施以避免递归。