Angular2 Observable - 在继续之前等待多个函数调用 [英] Angular2 Observable - Await multiple function calls before proceeding

问题描述

我正在尝试通过迁移当前用 Angular1/AngularJS 编写的应用程序来提高我对 Angular2 的了解.

I am trying to improve my knowledge of Angular2 by migrating an application currently written in Angular1/AngularJS.

特别是一个功能让我难住了.我正在尝试复制一个功能，其中调用函数等待继续，直到它调用的函数完成一个承诺循环.在 AngularJS 中，我调用的函数基本上是这样的:

One feature in particular has me stumped. I am trying to replicate a feature where a calling function waits to proceed until the function it is calling has completed a loop of promises. In AngularJS, the function I am calling looks basically like this:

this.processStuff = function( inputarray, parentnodeid ) {
    var promises = [];
    var _self = this;
    angular.forEach( inputarray , function( nodeid ) {

        switch ( parentnodeid )
        {
            case ‘AAA’ : var component = _self.doMoreStuff( nodeid, parentnodeid ); break;
            case ‘BBB’ : var component = _self.doMoreStuff( nodeid, parentnodeid ); break;
            case ‘CCC’ : var component = _self.doMoreStuff( nodeid, parentnodeid ); break;
            default    : var component = null;
        }
        promises.push( component );
    });
    return $q.all(promises);
}; 

它包含一个 forEach 循环，该循环调用另一个函数 (doMoreStuff)，该函数也返回一个承诺，并将所有这些返回的承诺存储在一个数组中.

It contains a forEach loop that calls another function (doMoreStuff) that also returns a promise, and it stores all those returned promises in an array.

使用 AngularJS，当我在另一个函数中调用 processStuff 时，我可以指望系统等待 processStuff 完成，然后再进入 then 块中的代码:

With AngularJS, when I call processStuff in another function, I could count on the system waiting until processStuff completed before entering into the code in the then block:

service.processStuff( arraying, parentidarg )
       .then(function( data ) {
              ... 

processStuff 的调用者等待所有 doMoreStuff 调用完成，直到 processStuff 的调用者进入它的 then> 阻止.

The caller of processStuff waits for all doMoreStuff invocations to complete until the caller of processStuff enters into its then block.

我不确定如何使用 Angular2 和 Observables 实现这一点.我可以从这些帖子中看到，为了模仿承诺，Observables 基本上只是使用 subscribe() 而不是 then():

I am unsure of how to achieve this with Angular2 and Observables. I can see from these posts that to mimic promises, Observables basically just use subscribe() instead of then():

Angular 1.x $q 到 Angular 2.0 beta

但是如何在应用程序继续之前等待 forEach 循环中的所有调用完成?

But how do I await all invocations in the forEach loop to complete before my application can proceed?

推荐答案

我一直在用 forkJoin 做这个

I have been doing this with forkJoin

import {Observable} from 'rxjs/Observable';
import 'rxjs/add/observable/forkJoin';

Observable.forkJoin(
  this.http.get('./friends.json').map((res: Response) => res.json()),
  this.http.get('./customer.json').map((res: Response) => res.json())
)
.subscribe(res => this.combined = {friends: res[0].friends, customer: res[1]});

这里有更多信息:http://www.syntaxsuccess.com/viewarticle/angular-2.0-and-http

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