angular - Observable 因错误而关闭

Question

我对 Angular 2 中的 Observable 有疑问。

我将我的组件订阅到一个可观察对象，然后当我的服务有新值时，我的组件会收到通知。
问题是当观察者推送错误时，比如 HTTP 错误，我的 observable 被关闭，所以我的组件不再收到通知。

问题
我怎样才能让我的组件在出现错误时继续监听我的服务？

例子
这里是example

这里是我的代码:

组件

constructor(private appService: AppService) {
    //I subscribe my component to an observable
    this.appService.commentsObservable.subscribe((comments) => {
        console.log(comments);
    }, (err) => {
        console.log(err);
    });
}

getComments() {
    //I ask the service to pull some comments
    this.appService.getComments()
}

服务

private commentsObserver: Observer<any>;
commentsObservable: Observable<any>;

constructor() {
    this.commentsObservable = new Observable((observer) => {
        this.commentsObserver = observer;
    });
}

getComments() {
    setTimeout(() => {
        //You will see the result displayed by the component
        this.commentsObserver.next([]);
    }, 0);

    setTimeout(() => {
        //You will see the result displayed by the component
        this.commentsObserver.next([]);
    }, 500);

    setTimeout(() => {
        //You will see the error displayed by the component
        this.commentsObserver.error({_body: 'Nice errroorr'});
    }, 1000);

    setTimeout(() => {
        //You won't see this one, why ?
        this.commentsObserver.next([]); 
    }, 1500);
}

Answer 1

这是预期的行为。 According to the documentation ,

In an Observable Execution, zero to infinite Next notifications may be delivered. If either an Error or Complete notification is delivered, then nothing else can be delivered afterwards.

对于上面的代码，可能是

this.appService
// error is caught, but the observable is completed anyway
.catch((err) => {
    console.error(err)
    return Observable.empty();
})
// re-subscribe to completed observable
.repeat()
.subscribe((comments) => console.log(comments));

但是考虑到预期的行为，使用 RxJS 错误处理来提供具有非关键错误值的连续可观察值是不切实际的。相反，它可能会更改为

setTimeout(() => {
    //You will see the error displayed by the component
    this.commentsObserver.next(new Error('Nice errroorr'));
}, 1000);

和

this.appService.commentsObservable.subscribe((comments) => {
    if (comments instanceof Error)
        console.error(comments);
    else
        console.log(comments);
});

方法可能因实际情况而异。