Javascript Angular2 Observable - 如何在继续之前等待循环中的所有函数调用结束？
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Angular2 Observable - how to wait for all function calls in a loop to end before proceeding?
提问by Benjamin McFerren
I am trying to improve my knowledge of Angular2 by migrating an application currently written in Angular1
我正在尝试通过迁移当前用 Angular1 编写的应用程序来提高我对 Angular2 的了解
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 angular one the function I am calling looks basically like this:
特别是一个功能让我难倒。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。在角度一中，我调用的函数基本上是这样的：
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);
};
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.
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。
With Angular1, 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. IE:
使用 Angular1，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。IE：
service.processStuff( arraying, parentidarg )
.then(function( data ) {
...
The caller of processStuffwaits for all doMoreStuffinvocations to complete until the caller of processStuffenters into its then block.
的调用者processStuff等待所有doMoreStuff调用完成，直到调用者processStuff进入其 then 块。
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:
我不确定如何使用 Angular2 和 Observables 来实现这一点。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：
Angular 1.x $q to Angular 2.0 beta
Angular 1.x $q 到 Angular 2.0 测试版
But how do I wait for all invocations in the forEachloop to complete before my system can proceed?
但是我如何forEach在系统可以继续之前等待循环中的所有调用完成？
回答by TGH
I have been doing this with forkJoin
我一直在用 forkJoin 做这个
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]});
Some more info here: http://www.syntaxsuccess.com/viewarticle/angular-2.0-and-http
这里有更多信息：http: //www.syntaxsuccess.com/viewarticle/angular-2.0-and-http
