Angular RxJS Poll实时数据switchMap类型错误

Question

我正在尝试使用 interval 和 switchMap 从我的服务器使用 RxJS 轮询实时数据。当用户导航到组件时，它将触发轮询。我通过使用以下服务代码直接请求 HTTP 端点（而不是扩展基础 class）来使其工作。

myService.ts:

public getRealTimeData() {
    return interval(5000).pipe(
      switchMap(() => {
        return this.httpClient.get('http://myendpoint:3000/endpoint');
      }),
      catchError((err) => {
        console.log('Handling error locally and rethrowing it...', err);
        return throwError(err);
      })
    );
  }

但是，我无法理解为什么当我扩展基本服务 class 并在基本服务中做同样的事情时 class 它给我一个错误

myService.ts:

...
constructor(){
    super(httpClient, 'my_custom_route')
}

public getRealTimeDataExtendingBaseClass() {
    return interval(5000).pipe(
      switchMap(() => {
        this.requestURLBase();
      }),
      catchError((err) => {
        console.log('Handling error locally and rethrowing it...', err);
        return throwError(err);
      })
    );
}

baseService.ts:

protected baseUrlPrefix = 'api/v1/';
constructor(protected httpClient: HttpClient, route: string) {
   this.route = route;
}

...

public requestURLBase() {
   return this.httpClient.get(this.baseUrlPrefix + this.url); 
}

这是错误堆栈：

errors.ts:30 ERROR TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.
    at Object.exports.subscribeTo (subscribeTo.ts:27)
    at Object.subscribeToResult (subscribeToResult.ts:36)
    at SwitchMapSubscriber._innerSub (switchMap.ts:139)
    at SwitchMapSubscriber._next (switchMap.ts:128)
    at SwitchMapSubscriber.Subscriber.next (Subscriber.ts:99)
    at AsyncAction.dispatch (interval.ts:75)
    at AsyncAction._execute (AsyncAction.ts:122)
    at AsyncAction.execute (AsyncAction.ts:97)
    at AsyncScheduler.flush (AsyncScheduler.ts:58)
    at ZoneDelegate.invokeTask (zone.js:421)

Answer 1

您忘记了请求流的 return。

switchMap(() => {
  return this.requestURLBase(); // <- return!!!
}),

Angular RxJS Poll实时数据switchMap类型错误

Angular RxJS Poll real-time data switchMap type error

httpclient

rxjs

angular