import { Operator } from '../Operator'; import { Subscriber } from '../Subscriber'; import { Observable } from '../Observable'; import { Subject } from '../Subject'; import { Subscription } from '../Subscription'; import { OuterSubscriber } from '../OuterSubscriber'; import { InnerSubscriber } from '../InnerSubscriber'; import { subscribeToResult } from '../util/subscribeToResult'; import { OperatorFunction } from '../types'; /** * Branch out the source Observable values as a nested Observable using a * factory function of closing Observables to determine when to start a new * window. * * It's like {@link bufferWhen}, but emits a nested * Observable instead of an array. * * ![](windowWhen.png) * * Returns an Observable that emits windows of items it collects from the source * Observable. The output Observable emits connected, non-overlapping windows. * It emits the current window and opens a new one whenever the Observable * produced by the specified `closingSelector` function emits an item. The first * window is opened immediately when subscribing to the output Observable. * * ## Example * Emit only the first two clicks events in every window of [1-5] random seconds * ```ts * import { fromEvent, interval } from 'rxjs'; * import { windowWhen, map, mergeAll, take } from 'rxjs/operators'; * * const clicks = fromEvent(document, 'click'); * const result = clicks.pipe( * windowWhen(() => interval(1000 + Math.random() * 4000)), * map(win => win.pipe(take(2))), // each window has at most 2 emissions * mergeAll() // flatten the Observable-of-Observables * ); * result.subscribe(x => console.log(x)); * ``` * * @see {@link window} * @see {@link windowCount} * @see {@link windowTime} * @see {@link windowToggle} * @see {@link bufferWhen} * * @param {function(): Observable} closingSelector A function that takes no * arguments and returns an Observable that signals (on either `next` or * `complete`) when to close the previous window and start a new one. * @return {Observable>} An observable of windows, which in turn * are Observables. * @method windowWhen * @owner Observable */ export function windowWhen(closingSelector: () => Observable): OperatorFunction> { return function windowWhenOperatorFunction(source: Observable) { return source.lift(new WindowOperator(closingSelector)); }; } class WindowOperator implements Operator> { constructor(private closingSelector: () => Observable) { } call(subscriber: Subscriber>, source: any): any { return source.subscribe(new WindowSubscriber(subscriber, this.closingSelector)); } } /** * We need this JSDoc comment for affecting ESDoc. * @ignore * @extends {Ignored} */ class WindowSubscriber extends OuterSubscriber { private window?: Subject; private closingNotification?: Subscription; constructor(protected destination: Subscriber>, private closingSelector: () => Observable) { super(destination); this.openWindow(); } notifyNext(_outerValue: T, _innerValue: any, _outerIndex: number, _innerIndex: number, innerSub: InnerSubscriber): void { this.openWindow(innerSub); } notifyError(error: any): void { this._error(error); } notifyComplete(innerSub: InnerSubscriber): void { this.openWindow(innerSub); } protected _next(value: T): void { this.window!.next(value); } protected _error(err: any): void { this.window!.error(err); this.destination.error(err); this.unsubscribeClosingNotification(); } protected _complete(): void { this.window!.complete(); this.destination.complete(); this.unsubscribeClosingNotification(); } private unsubscribeClosingNotification(): void { if (this.closingNotification) { this.closingNotification.unsubscribe(); } } private openWindow(innerSub: InnerSubscriber | null = null): void { if (innerSub) { this.remove(innerSub); innerSub.unsubscribe(); } const prevWindow = this.window; if (prevWindow) { prevWindow.complete(); } const window = this.window = new Subject(); this.destination.next(window); let closingNotifier; try { const { closingSelector } = this; closingNotifier = closingSelector(); } catch (e) { this.destination.error(e); this.window.error(e); return; } this.add(this.closingNotification = subscribeToResult(this, closingNotifier)); } }