Observable forkJoin 不触发 [英] Observable forkJoin not firing

问题描述

我正在尝试在两个 Observable 上使用 forkJoin.其中一个以流的形式开始...如果我直接订阅它们，我会收到回复，但 forkJoin 不会触发.有什么想法吗?

I'm trying to use forkJoin on two Observables. One of them starts as a stream... If I subscribe to them directly I get a response, forkJoin isn't firing though. Any ideas?

private data$: Observable<any[]>;
private statuses$: Observable<any[]>;
private queryStream = new Subject<string>();    

....

this.data$ = this.queryStream
    .startWith('')
     .flatMap(queryInput => {
            this.query = queryInput
            return this._companyService.getCompanies(this.queryRequired + ' ' + this.query, this.page, this.sort);
                })
            .share();
    
...

Observable.forkJoin(this.statuses$, this.companies$)
            .subscribe(res => {
                console.log('forkjoin');
                this._countStatus(res[0], res[1]);
            });


// This shows arrays in the console...

this.statuses$.subscribe(res => console.log(res));
this.companies$.subscribe(res => console.log(res));

// In the console
Array[9]
Array[6]

推荐答案

forkJoin 的一个很常见的问题是它要求所有源 Observables 至少发出一项，并且所有这些都必须完成.

A very common problem with forkJoin is that it requires all source Observables to emit at least one item and all of them have to complete.

换句话说，如果 this.statuses$ 或 this.companies$ 不发出任何项目，直到它们都完成 forkJoin不会发出任何东西.

In other words if this.statuses$ or this.companies$ doesn't emit any item and until they both complete the forkJoin won't emit anything.

this.statuses$.subscribe(
    res => console.log(res),
    undefined,
    () => console.log('completed'),
);

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