如何在ngrx效果中进行http轮询 [英] How to do http polling in ngrx effect

问题描述

我有这种效果，我正在尝试使用计时器每x秒轮询一次数据.但是我无法弄清楚计时器应该如何与数据流交互.我尝试在顶部添加另一个switchMap，但是后来我无法将操作和有效负载传递给第二个switchmap.有什么想法吗?

I have this effect, and I'm trying to use timer to poll for data every x seconds. But I can't figure out how timer is supposed to interact with the data streams. I tried adding another switchMap to the top, but then I couldn't pass the action and payload to the second switchmap. Any ideas?

我查看了这篇文章但是我的情况有些不同.我正在通过需要访问的操作传递有效负载，并且正在使用ngrx 6.

I looked at this post but my situation is a little different. I'm passing a payload with my action that I need to access, and I'm using ngrx 6.

@Effect()
getData = this.actions$
    .ofType(appActions.GET_PLOT_DATA)
    .pipe(
        switchMap((action$: appActions.GetPlotDataAction) => {
            return this.http.post(
                `http://${this.url}/data`,
                action$.payload.getJson(),
                {responseType: 'json', observe: 'body', headers: this.headers});
        }),
        map((plotData) => {
            return {
                type: appActions.LOAD_DATA_SUCCESS,
                payload: plotData
            }
        }),
        catchError((error) => throwError(error))
    )

推荐答案

这应该有效(我已经对其进行了测试).请在switchMap的顶部添加.此处的关键操作员是mapTo.该运算符会将间隔的输入值映射到有效负载中.

This should work (i have tested it). Please add this top of the switchMap. The key operator here is the mapTo. This operator will map the incoming value of the interval into the payload.

switchMap((action$: appActions.GetPlotDataAction) =>
   interval(5000).pipe(mapTo(action$))
);

更新(提示): -如果要立即开始轮询，然后每{n} ms开始，可以使用startWith运算符或timer observable

Update (hint): - If you want to start immediately with the polling and then each {n}ms you can use the startWith operator or the timer observable

switchMap((action$: appActions.GetPlotDataAction) =>
  interval(5000).pipe(startWith(0), mapTo(action$))
);

或

switchMap((action$: appActions.GetPlotDataAction) => 
  timer(0, 1000).pipe(mapTo(action$))
);

这篇关于如何在ngrx效果中进行http轮询的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！