在继续执行另一个函数之前等待所有 HTTP 请求返回

Question

我想等待三个 HTTP 请求完成，然后再调用另一个函数来处理三个 HTTP 请求返回的数据。

我尝试循环房间数（相当于所需的 HTTP 请求数），然后将设备推送到数组中。在将设备数组传递给下一个要处理的函数之前，我需要完成所有三个 HTTP 请求。

getDeviceListByRoom(rooms_id_array: string[]) {
    console.log('The rooms_id_array is: ', rooms_id_array);
    this.room_device_map = new Map;
    let count = 0;
    for (const id of rooms_id_array) {
      const devicesByRoom = this.Services.getDeviceByRoom(id);
      devicesByRoom.subscribe((res: any) => {
        if (res.code === 200) {
          // this statement will map the list of devices to the room.
          this.room_device_map.set(id, res.data);

          // this statement will just push the list of devices from different room into one array.
          this.all_devices_list.push(res.data);
          console.log('count is: ', count++);
        }
      }, err => {
        console.error('ERROR', err);
      });
      console.log('In all_devices_list is: ', this.all_devices_list);
    }
    console.log('Lalalalal');
  }

The code above will return 'Lalalala' first followed by the console print out of the count variable. Understandably, the for...of function is non blocking...?

Answer 1

forkJoin 是你的朋友。

（我在手机上，对不起我的简短）

Answer 2

最简单的方法是“forkJoin”，在这种情况下，您也可以使用“zip”或“combineLatest”。

试试这个：

import { forkJoin } from 'rxjs';

...

let req1 = this.http.get('xxx');
let req2 = this.http.get('yyy');

forkJoin([req1, req2]).subscribe(res => {
    // res[0] is from req1
    // res[1] is from req2
});

Answer 3

所有 3 个请求都发出后，Combine latest 将发出

combineLatest(
  this.http.get('request1'),
  this.http.get('request2'),
  this.http.get('request3')
).subscribe(([response1, response2, response3]) => {
  // Here you can do stuff with response1, response2 and response3
});