Node.js 如何等待异步HTTP请求返回Angular 4上的值？

我有一些“卡片”，我想在Angular服务上为他们获取信息，问题是我通过API上的http请求获取这些信息，我想在所有请求完成后返回

卡片.组件.ts 卡片服务 当它运行时，如果它应该有一个整数，则会出现：

[对象]

如果我试图将return语句放入subscribe函数中，“cards.component.ts”会给出以下错误：

类型“void”不可分配给类型“Object[]”

---

http请求正确完成后，如何返回卡信息？

您应该在

getData（）

方法中返回observable，然后在组件中订阅。通过这种方式，组件知道可观察对象何时完成（在subscribe方法中）

import {Component} from '@angular/core';

import {CardsService} from './cards.service';

import 'easy-pie-chart/dist/jquery.easypiechart.js';

@Component({
  selector: 'cards',
  templateUrl: './cards.html',
  styleUrls: ['./cards.scss']
})
// TODO: move easypiechart to component
export class Cards {

  public charts: any;

  constructor(private _cardsService: CardsService) {
    this.charts = this._cardsService.getData();
  }
}

import {Injectable} from '@angular/core';
import {BaThemeConfigProvider, colorHelper} from '../../../theme';
import { Http, Headers, Response } from '@angular/http';
import {Observable} from "rxjs/Observable";

@Injectable()
export class CardsService {
  _meterCountURL = 'http://localhost:8080/meter/count';
  _cardMeter;
  _cardConsumption;
  constructor(private _baConfig:BaThemeConfigProvider, private http: Http) {
  }

  getData() {
    let pieColor = this._baConfig.get().colors.custom.dashboardPieChart;

    let headers = new Headers({'Content-type': 'application/x-www-form-urlencoded',
                               'Authorization': 'Bearer ' + localStorage.getItem('id_token')});

    Observable.forkJoin(
      this.http.get(this._meterCountURL, {headers: headers}).map((response) => {response.json()['data'];}),
      this.http.get(this._meterCountURL, {headers: headers}).map((response) => {response.json()['data'];})
    ).subscribe(
      data => {
        this._cardMeter = data[0];
        this._cardConsumption = data[1];
      },
      error => console.log(error)
    );

    return [
        color: pieColor,
        description: 'Consumo do mês atual',
        stats: 0 || this._cardConsumption,
        icon: 'ion-flash',
      }, {
        color: pieColor,
        description: 'Número de unidades ativas',
        stats: 0 || this._cardMeter,
        icon: 'ion-ios-speedometer',
      }
    ];
  }
}

// card.service.ts
getData() {
    return Observable.forkJoin(...);
}

// cards.component.ts
this._cardsService.getData().subscribe(data => {
    this.charts = ...;
});