Question

当我尝试合并observbles时，我收到错误You provided 'undefined' where a stream was expected.。

我在这里创建我的刷新observable：

refresh$: Observable<Funnel[]>;

然后我有一个计时器......

TimerObservable.create(0, (this.storageService.refRate * 1000))
    .takeWhile(() => this.interval)
    .subscribe(() => {
        this.refresh$ = this.funnelService.getStoryFunnels({}).map(response => [...response]);
    });

然后当我尝试合并observable时，会产生错误：

this.funnels$ = this.funnelService.getStoryFunnels({}).pipe(
    merge(this.refresh$, funnelCreation$.pipe(
            filter(funnel => !!funnel),
            map(funnel => [funnel])
        )
    )
);

基于舒适的回答进行更新：

this.refresh$ = TimerObservable.create(0, (this.storageService.refRate * 500))
    .takeWhile(() => this.interval)
    .switchMap(() =>  this.funnelService.getStoryFunnels({}).map(response => [...response]));

然后：

this.funnels$ = this.funnelService.getStoryFunnels({}).pipe(
        merge(this.refresh$, funnelCreation$.pipe(
                filter(funnel => !!funnel),
                map(funnel => [funnel])
            )
        )
    );

Answer 1

这是因为this.funnels$ 在声明时不是可观察的（不是用任何值启动），因为它只会在定时器之后才被赋值被执行。然而，声明代码几乎立即执行（同步）。这就是为什么你得到undefined。

您应该使用switchMap并将this.refresh$分配给它：

this.refresh$ = TimerObservable.create(0, (this.storageService.refRate * 1000))
    .takeWhile(() => this.interval)
    .switchMap(() =>  this.funnelService.getStoryFunnels({}).map(response => [...response]));

rxjs merge：你提供了＆＃39; undefined＆＃39;预期流的地方

1 个答案: