等待一个可观察的事物完成

问题描述

我有一个方法需要等待可观察对象完成.我知道Observable对于随着时间的推移返回单个数据非常有用，但是我需要知道何时该Observable完全完成了所有数据的返回，以便我可以在返回的对象上运行验证代码.

I have a method that needs to wait for an observable to finish. I know observable are great for returning single pieces of data over time but I need to know when this observable has completely finished returning all of its data so I can run validation code on the object it has returned.

getCustom方法订阅在提供的url上的可观察的运行，然后返回可观察的.

The method getCustom subscribes to an observable run on the supplied url which then returns the observable.

我不太确定这是否是解决这种情况的最佳方法，因此，如果有人可以给我任何建议或指导来解决这个问题，我将不胜感激.

I am not too sure if this is the best way to approach this situation so I would appreciate if anyone could give me any advice or a direction to handle this.

  private validateQuoteRetrievalAnswers(reference: string) {

         // Get the risk from the server
        this.riskManager.getRiskFromServer(reference);

        if (this.riskManager.risk) {
            // Validate risk that was returned
        }
    }

getRiskFromServer(quoteReference: string) {

    this.riskService.getCustom("Url").subscribe => {
        // need to know when the observable has returned the risk
    });

}

推荐答案

我将如何应对这一挑战:

how i would tackle this challenge:

查询您的后端，当我们有需要时将其推送到主题

Query you back-end and when we've got what we need push it to a Subject

riskSubject = new Subject<Risk>();

getRiskFromServer(quoteReference: string) {
  this.riskService.getCustom("Url")
  .subscribe(
    data => { this.riskSubject.next(data); },
    error => { console.log(error) }
 });
}

然后订阅主题并等待，直到获得所需的内容并开始验证

and then subscribe to subject and wait until you get what you need and start validating

private validateQuoteRetrievalAnswers(reference: string) {

         // Get the risk from the server
        this.riskManager.getRiskFromServer(reference);
        // subscribe to subject
        this.riskManager.riskSubject.subscribe(
         data => {
           //do your validation
        })
}

主题不过是传统的事件总线，而功能却强大得多，因为它为所有RxJs功能运算符提供了它.但从本质上讲，我们只是像常规的可观察对象一样使用它来进行订阅

The subject is nothing more than a traditional event bus, but much more powerful as it provides all the RxJs functional operators with it. But at its heart, we simply use it to subscribe just like a regular observable

来源: angular-university.io

或者您可以使用Observable.fromPromise(promise)，但是如果您是ng2的新手，那么这会使事情变得更加复杂

OR you can use Observable.fromPromise(promise) but this will make things a bit more complicated to understand if you are new to ng2

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