Question

我正在构建一个通知组件，该组件应向用户显示通知。一次创建多个通知时，应将它们排队。

现在，它可以很好地显示第一个通知，但之后它会同时触发2条通知（请参见下面的当前输出）。它不等待上一个通知显示，然后再次隐藏再显示下一个通知。

notifications.api.ts ：

public notifications = new Subject<INotificationEvent>();
public notifications$ = this.notifications.asObservable();

notifications.component.ts ：

private finished = new Subject();

constructor(private notifications: NotificationsApi) {}

zip(this.notificationsApi.notifications$, this.notificationsApi.notifications, (i, s) => s).pipe(
  tap(() => {

    if (!this.isActive) {
      this.finished.next();
    }
  }),
  delayWhen(() => this.finished),
  delay(450),
  tap((event: INotificationEvent) => {
    this.notification = event;
    this.isActive = true;
    this.cd.markForCheck();
    console.log(this.notification);
    console.log('showing');
  }),
  delay(this.hideAfter),
  tap(() => {
    this.isActive = false;
    this.cd.markForCheck();
    console.log('closing');
  }),
  delay(450)
).subscribe(() => {
  console.log('finishing');
  this.finished.next();
});

app.component.ts ：

let i = 0;
setInterval(() => {
  this.notifications.newNotification({message: `${i}`, theme: 'primary'});
  i++;
}, 2000);

当前输出：

{message: "0", theme: "primary"}
showing
closing
finishing
{message: "1", theme: "primary"}
showing
{message: "2", theme: "primary"}
showing
closing
finishing
{message: "3", theme: "primary"}
showing
{message: "4", theme: "primary"}
showing
closing
closing
finishing
finishing
{message: "5", theme: "primary"}
showing
{message: "6", theme: "primary"}

所需的输出：

{message: "0", theme: "primary"}
showing
closing
finishing
{message: "1", theme: "primary"}
showing
closing
finishing
{message: "2", theme: "primary"}
showing
closing
finishing
{message: "3", theme: "primary"}
showing
closing
finishing
{message: "4", theme: "primary"}
showing
closing
finishing
{message: "5", theme: "primary"}
showing
closing
finishing
{message: "6", theme: "primary"}
showing
closing
finishing

我该如何解决？

Answer 1

根据您的描述，在我看来，@PostConstruct和concatMap可以轻松实现相同目标。

在此示例中，每次单击按钮都代表一个通知。每个通知需要2秒。这取决于您要在观察者中执行的操作，但是如果您根本不需要该通知，则可以将其留空（否则可能需要delay）。多条通知在startWith中排队，并一个接一个地执行。

concatMap

实时演示：https://stackblitz.com/edit/rxjs-nqtfzm?file=index.ts

Angular / RxJS-将流延迟到上一个流完成

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