Question

我在for循环中有一个订阅，它从外部源获取JSON数据作为一系列“类别数据”，然后根据用户当前位置过滤该数据。我需要的是等待所有订阅完成，然后才能继续我的应用程序。现在，它不会等待所有订阅完成，它只完成一些订阅，然后继续，而其他订阅在后台继续。

我尝试了以下“强力”方法，我知道将在已过滤的数组中添加一定数量的类别，但它可以正常工作，但我不知道如何使其适用于任何情况。

这是我的代码：

getMultipleCategoryData(categoryIds: string[]) {
for (let i = 0; i < this.waypointIds.length; i++) {
//after user selects their categories, its added to waypointNames, and occurences() gets the # of occurences of each waypoint name
  let occurences = this.occurences(this.waypointNames[i], this.waypointNames);
  this.categoryApi.getCategoryData(this.waypointIds[i]).toPromise().then(data => {

    let filteredLocs = data.locations.filter(loc => this.distanceTo(loc, this.hbLoc) < MAX_RADIUS);
    let foundLocs = [];
    //fill filteredLocs with first n, n = occurences, entries of data 
    for (let n = 0; n < occurences; n++) {
      if (filteredLocs[n] != undefined) {
        foundLocs[n] = filteredLocs[n];
      }
    }
    //find locations closest to hbLoc (users current location), and add them to waypoints array
    for (let j = 0; j < foundLocs.length; j++) {
      for (let k = 0; k < filteredLocs.length; k++) {
        if (this.distanceTo(this.hbLoc, filteredLocs[k]) < this.distanceTo(this.hbLoc, foundLocs[j]) && foundLocs.indexOf(filteredLocs[k]) < 0) {
          foundLocs[j] = filteredLocs[k];
        }
      }
    }
    if (foundLocs.length > 0 && foundLocs.indexOf(undefined) < 0) {
      for (let m = 0; m < foundLocs.length; m++) {
        this.waypointLocs.push(foundLocs[m]);
      }
    }
  }).then(() => { 
    //this hardcoded, brute force method works, but i'd need it to be more elegant and dynamic
    if (this.waypointLocs.length >= 5) {
      let params = { waypointLocs: this.waypointLocs, hbLoc: this.hbLoc };
      this.navCtrl.push(MapPage, params);
    }
  });
}
}

categoryApi.getCategoryData方法：

getCategoryData(categoryId): Observable<any> {
    // don't have data yet
    return this.http.get(`${this.baseUrl}/category-data/${categoryId}.json`)
        .map(response => {
            this.categoryData[categoryId] = response.json();
            this.currentCategory = this.categoryData[categoryId];
            return this.currentCategory;
        });
}

一切正常，除非等待订阅完成，我真的想要一种确定所有订阅何时完成的方法。任何帮助表示赞赏！

Answer 1

您可以收集数组中的所有可观察对象，并使用forkJoin等待所有这些对象完成：

let observables: Observable[] = [];
for (let i = 0; i < this.waypointIds.length; i++) {
    observables.push(this.categoryApi.getCategoryData(this.waypointIds[i]))
}
Observable.forkJoin(observables)
    .subscribe(dataArray => {
        // All observables in `observables` array have resolved and `dataArray` is an array of result of each observable
    });

如何在继续之前等待for循环内的订阅完成

1 个答案: