Question

我知道activatedRoute实际上是BehaviourSubject，但是由于它的公开API是可以观察到的，所以我不想冒险。

activatedRoute.queryParams.pipe(
    take(1),
).subscribe(query => {  // { page?: '1' | '2' | '3'... }
    this.currentPage = new BehaviourSubject(+(query.page) || 1);
    // Other components actually change this
});

console.log(this.currentPage); // I need this to not be undefined!

是否存在类似的管道？ takeSynchonously(1, { page: 1 })

Answer 1

我找到了答案，它是takeUntil，timer和queueScheduler的组合。

const { BehaviorSubject, ReplaySubject, Subject, timer, queueScheduler } = rxjs;
const { startWith, defaultIfEmpty, takeUntil, take } = rxjs.operators;

new Subject().pipe(
  take(1),
  takeUntil(timer(1, queueScheduler)),
  defaultIfEmpty(0),
).subscribe(n => console.log('Subject', n));

new ReplaySubject(1).pipe(
  take(1),
  takeUntil(timer(1, queueScheduler)),
  defaultIfEmpty(0),
).subscribe(n => console.log('ReplaySubject', n));

const rs = new ReplaySubject(1);
rs.next(1)
rs.pipe(
  take(1),
  takeUntil(timer(1, queueScheduler)),
  defaultIfEmpty(0),
).subscribe(n => console.log('ReplaySubject (with value)', n));

new BehaviorSubject(5).pipe(
  take(1),
  takeUntil(timer(1, queueScheduler)),
  defaultIfEmpty(0),
).subscribe(n => console.log('BehaviorSubject', n));

console.log('priority')

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/6.5.2/rxjs.umd.js"></script>

注意：该选项必须与ReplySubject或类似名称结合使用。具有初始值的所有内容都是同步的，但是没有初始值的任何内容都将在下一个滴答中处理。

如果同步，RXJS取1，否则使用defaultValue

1 个答案: