­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ import { Observable } from '../Observable'; import { MonoTypeOperatorFunction } from '../types'; import { operate } from '../util/lift'; import { OperatorSubscriber } from './OperatorSubscriber'; import { innerFrom } from '../observable/from'; import { noop } from '../util/noop'; /** * Returns an Observable that skips items emitted by the source Observable until a second Observable emits an item. * * The `skipUntil` operator causes the observable stream to skip the emission of values ​​until the passed in observable emits the first value. * This can be particularly useful in combination with user interactions, responses of http requests or waiting for specific times to pass by. * * ![](skipUntil.png) * * Internally the `skipUntil` operator subscribes to the passed in observable (in the following called *notifier*) in order to recognize the emission * of its first value. When this happens, the operator unsubscribes from the *notifier* and starts emitting the values of the *source* * observable. It will never let the *source* observable emit any values if the *notifier* completes or throws an error without emitting * a value before. * * ## Example * * In the following example, all emitted values ​​of the interval observable are skipped until the user clicks anywhere within the page. * * ```ts * import { interval, fromEvent } from 'rxjs'; * import { skipUntil } from 'rxjs/operators'; * * const intervalObservable = interval(1000); * const click = fromEvent(document, 'click'); * * const emitAfterClick = intervalObservable.pipe( * skipUntil(click) * ); * // clicked at 4.6s. output: 5...6...7...8........ or * // clicked at 7.3s. output: 8...9...10..11....... * const subscribe = emitAfterClick.subscribe(value => console.log(value)); * ``` * * @param {Observable} notifier - The second Observable that has to emit an item before the source Observable's elements begin to * be mirrored by the resulting Observable. * @return A function that returns an Observable that skips items from the * source Observable until the second Observable emits an item, then emits the * remaining items. */ export function skipUntil(notifier: Observable): MonoTypeOperatorFunction { return operate((source, subscriber) => { let taking = false; const skipSubscriber = new OperatorSubscriber( subscriber, () => { skipSubscriber?.unsubscribe(); taking = true; }, noop ); innerFrom(notifier).subscribe(skipSubscriber); source.subscribe(new OperatorSubscriber(subscriber, (value) => taking && subscriber.next(value))); }); }