等待订阅完成 [英] Wait for subscription to complete

问题描述

我有一个简单的场景: 我想将服务返回的数组存储到类变量中.在存储数据之前，如何等待数据可用?如果我等待一定时间(使用settimeout测试)，则可以使用此功能.

I have a simple scenario: I want to store an array returned from a service into a class variable. How do I wait for the data to be available until I store the data? It is available if I wait a certain amount of time (tested with settimeout) .

服务:

  public getEventHistory(): Observable<heatmapElement[]> {

return this.tokenResolver.getToken(true).switchMap(token => {
  var headers = new Headers();
  headers.append('Authorization', 'Bearer ' + token);
  headers.append('Content-Type', 'application/json');

  return this.http.get(this.restApi, new RequestOptions({headers: headers}));
})     
.map((res: Response) => res.json());
}

客户订阅:

getEventHistory(): void {
this.eventHistoryService.getEventHistory()
                        .subscribe(data =>  this.heatmapData = data,
                                   error => console.log('Error in Heatmap get data: ' + <any> error)
                        );

console.log('HeatmapData: '+ this.heatmapData.toString()); <---- Undefined and causes error
}

如果我等了一段时间，数据就可用了...但是这样就没必要了……

The data is available if I wait some time... but that shouldn't be necessary in this way should it...

ngOnInit(): void {
    this.getEventHistory();
    setTimeout(() => {
      console.log('HeatmapData: '+ this.heatmapData.toString());
    },3000);
  }

推荐答案

您可以在complete()函数上执行此操作.这样做将确保数据首先到达.

You can just do it on complete() function. Doing that you will ensure that the data has arrived first.

    getEventHistory(): void {
    this.eventHistoryService.getEventHistory()
                            .subscribe(data =>  this.heatmapData = data,
                                       error => console.log('Error in Heatmap get data: ' + <any> error),
                                       () => console.log('HeatmapData: '+ this.heatmapData.toString());
                            );

    }

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