Angular：如何知道请求是否已在 HttpClient 中取消

Question

要知道请求是否已完成，我会这样做if (httpEvent instanceof HttpResponse)。同样，如何知道请求是否在 中被取消HttpInterceptor？下面是我的intercept功能。

intercept(httpRequest: HttpRequest<any>, httpHandler: HttpHandler): Observable<HttpEvent<any>> {
    this.requestsPending++;

    if (this.typeAheads.includes(httpRequest.url.split('/').pop()))
      this.slimLoadingBarService.start();
    else
      this.flsLoaderService.start();

    return httpHandler.handle(httpRequest)
      .do((httpEvent: HttpEvent<any>) => {
        if (httpEvent instanceof HttpResponse) {
          // decrementing counter on each request return
          this.requestsPending--;

          if (this.typeAheads.includes(httpEvent.url.split('/').pop())) {
            if (this.requestsPending === 0)
              this.slimLoadingBarService.complete();
          }
          else {
            if (this.requestsPending === 0)
              this.flsLoaderService.stop();
          }
        }
      }, () => {
        this.slimLoadingBarService.complete();

        // reset counter on error
        this.requestsPending = 0;
        this.flsLoaderService.stop();
      });
  }

Answer 1

我也遇到了这个问题，这是我最近想到的解决方案：

要知道请求是否被取消，您可以使用finally运算符，示例如下：

let cancelled = true;
return next.handle(request).do(
  undefined,
  () => {
    // error
    cancelled = false;
  },
  () => {
    // completed
    cancelled = false;
  },
).finally(
  () => {
    if (cancelled) {
      // do things
    }
  },
);

Answer 2

看起来 Angular 忽略了中止事件。这是角度来源：https://github.com/angular/angular/blob/5.0.1/packages/common/http/src/xhr.ts

如果请求被中止，返回的 Observable 不会通知订阅者。