如何在行为主题上抛出错误并继续流? [英] How do I throw an error on a behaviour subject and continue the stream?

问题描述

一方面，我有一个可能偶尔会抛出错误的流:

On one end, I have a stream which may occasionally throw an error:

this.behaviorSubject.error(error)

不过，稍后我想继续直播:

Later on, however, I want to continue the stream:

this.behaviorSubject.next(anotherValue)

另一方面，我有一个订阅者订阅了 behaviorSubject.asObservable().

on the other end, I have a subscriber subscribed to behaviorSubject.asObservable().

在订阅中，我正在处理值和错误:

In the subscribtion, I'm handling the value and the error:

.subscribe( 
   ( value ) =>  {  /* ok */ },
   ( error ) =>  {  /* some error */ }
);

我希望效果与简单的 onSuccess 和 onError 回调相同，其中每次发生错误时都会调用 onError 并且不会阻止将来进行 onSuccess 调用.我如何使用 RXJS 做到这一点?

I want the effect to be the same as a simple onSuccess and onError callback, where onError is called every time an error occurs and doesn't prevent future onSuccess calls from being made. How do I do this with RXJS?

我已经研究了 catch ，但它似乎只是防止在订阅者上调用错误.

I've looked into catch but it seems to just prevent error from being called on subscribers.

推荐答案

简短回答:不可能.

如何处理: RxJS 的基本概念是任何 error 或 complete 调用基本上都会杀死 一个流.这个概念迫使您不要随心所欲地到处抛出错误"，而是要正确处理应用程序中的错误和数据流.例如，BehaviorSubject 通常用于保存数据，但它不也应该用于包括检索/创建该数据的过程以及处理可能发生的错误数据的检索.

How to work with this: The basic concept of RxJS is that any error or complete-call will basically "kill" a stream. This concept forces you not "just to throw around errors here and there as you please" but to handle errors and the flow of data within your application properly. A BehaviorSubject for example is typically meant to hold data, however it should not be used to also include the process of retrieving/creating that data and handle possible errors that might occur during the retrieval of the data.

因此，如果您想循规蹈矩，您应该将流程分成两部分:

So if you want to go by the book, you should split up your flow into two parts:

1. 数据的检索/创建:一个流，将运行一次，然后在发生时完成和/或抛出错误.检索到数据后，会将其发送到商店.
2. 商店(例如在你的情况下:一堆 BehaviorSubjects):只有有效数据到达商店，这意味着这里没有进行错误处理，所有部分都依赖于商店可以相信商店拥有正确的数据.

1. Retrieval/creation of the data: A stream, that will run once then then completes and/or throws an error whenever one occurs. When the data is retrieved it will be sent to the store.
2. The store (e.g. as in your case: a bunch of BehaviorSubjects): Only valid data arrives in the store, this means that no error-handling is done here and all parts relying on the store can trust in the store that it holds the correct data.

<小时>

例如，您的数据流可能如下所示(粗略草图):

---

As an example your data flow could look as follows (as a rough sketch):

store.ts

dataStore: BehaviorSubject<IData> = new BehaviorSubject<IData>();
errorMessage: BehaviorSubject<IErrorMsg> = new BehaviorSubject<IErrorMsg>();

data-retrieval.ts

fetchDataById(id: string) {
    httpService.get(`some/rest/endpoint/${id}`)
        .subscribe(handleData, handleError);
}

handleData(data: IData) {
    errorMessage.next(null);
    dataStore.next(data);
}

handleError(error: Error) {
    errorMessage.next(error.message);
    dataStore.next(null);
}

<小时>

但这看起来像很多开销..." - 没错，但是它确保了应用程序中干净且易于理解的数据流，易于测试和维持.还有现成的商店概念，如 ngrx 或 redux 可以使用.

---

"But this looks like a lot of overhead..." - True, however it ensures a clean and easy-to-understand flow of data within your application, that is easy to test and maintain. Also there are ready-to-use store-concepts like ngrx or redux that could be used.

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