在两个独立的成功http请求后激发回调

Fire callback after two separate successful http requests

本文关键字：请求 http 回调 成功 独立 两个      更新时间：2023-09-26

init上我的应用程序的根组件从我的服务中调用两个异步函数来获取数据。我想知道如何在它们都完成后调用一个函数。我使用的是angular 2.0.0 alpha.44和typescript 1.7.3

import {Component, OnInit} from 'angular2/angular2';
import {ServiceA} from './services/A';
import {ServiceB} from './services/B';

@Component({
  selector: 'app',
  template: `<h1>Hello</h1>`
})
export class App {
  constructor(
    public serviceA: ServiceA,
    public serviceB: ServiceB
  ) { }
  onInit() {
    // How to run a callback, after 
    // both getDataA and getDataB are completed?
    // I am looing for something similar to jQuery $.when()
    this.serviceA.getDataA();
    this.serviceB.getDataB();
  }
}

serviceA.getDataA和serviceA.getDataB是简单的http获取函数：

// Part of serviceA
getDataA() {
  this.http.get('./some/data.json')
    .map(res => res.json())
    .subscribe(
      data => {
        // save res to variable
        this.data = data;
      },
      error => console.log(error),
      // The callback here will run after only one 
      // function is completed. Not what I am looking for.
      () => console.log('Completed')
    );
}

一个简单的仍然并行的解决方案应该是这样的：

let serviceStatus = { aDone: false, bDone: false };
 let getDataA = (callback: () => void) => {
     // do whatver.. 
     callback();
 }
 let getDataB = (callback: () => void) => {
     // do whatver.. 
     callback();
 }
 let bothDone = () => { console.log("A and B are done!");
 let checkServiceStatus = () => {
     if ((serviceStatus.aDone && serviceStatus.bDone) == true)
        bothDone();
 }
 getDataA(() => { 
     serviceStatus.aDone = true;
     checkServiceStatus(); 
});
getDataA(() => { 
     serviceStatus.bDone = true;
     checkServiceStatus(); 
});

我个人使用RxJS来让我摆脱这种棘手的情况，可能值得一看。

编辑：

给出RxJS实际使用的反馈：

let observable1: Rx.Observable<something>;
let observable2: Rx.Observable<something>;
let combinedObservable = Rx.Observable
    .zip(
        observable1.take(1), 
        observable2.take(1),
        (result1, result2) => {
            // you can return whatever you want here
            return { result1, result2 };
        });
combinedObservable
    .subscribe(combinedResult => {
        // here both observable1 and observable2 will be done.
    });

本例将并行运行两个可观察器，并在两者都完成后将结果合并为一个结果。

您可以在函数定义中传递getDataA和getDataB回调，然后按顺序调用任何您想要的：

function getDataA(callback) {
     // do some stuff
     callback && callback();
}
function getDataB(callback) {
     // do some stuff
     callback && callback();
}
function toCallAfterBoth() {
    // do some stuff
}
getDataA(getDataB(toCallAfterBoth));

您可以嵌套函数调用。

例如：

function getDataA (callback) {
    var dataA = {test:"Hello Data A"};
    callback && callback(dataA);
}
function getDataB (callback) {
    var dataB = {test:"Hello Data B"};
    callback && callback(dataB);
}
getDataA(function (dataA) {
    getDataB(function (dataB) {
        console.log("Both functions are complete and you have data:");
        console.log(dataA);
        console.log(dataB);
    });
});
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