77 lines
2.7 KiB
JavaScript
77 lines
2.7 KiB
JavaScript
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import { OuterSubscriber } from '../OuterSubscriber';
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import { subscribeToResult } from '../util/subscribeToResult';
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/**
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* Converts a higher-order Observable into a first-order Observable by dropping
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* inner Observables while the previous inner Observable has not yet completed.
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*
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* <span class="informal">Flattens an Observable-of-Observables by dropping the
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* next inner Observables while the current inner is still executing.</span>
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*
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* <img src="./img/exhaust.png" width="100%">
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*
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* `exhaust` subscribes to an Observable that emits Observables, also known as a
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* higher-order Observable. Each time it observes one of these emitted inner
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* Observables, the output Observable begins emitting the items emitted by that
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* inner Observable. So far, it behaves like {@link mergeAll}. However,
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* `exhaust` ignores every new inner Observable if the previous Observable has
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* not yet completed. Once that one completes, it will accept and flatten the
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* next inner Observable and repeat this process.
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*
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* @example <caption>Run a finite timer for each click, only if there is no currently active timer</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var higherOrder = clicks.map((ev) => Rx.Observable.interval(1000).take(5));
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* var result = higherOrder.exhaust();
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* result.subscribe(x => console.log(x));
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*
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* @see {@link combineAll}
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* @see {@link concatAll}
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* @see {@link switch}
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* @see {@link mergeAll}
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* @see {@link exhaustMap}
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* @see {@link zipAll}
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*
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* @return {Observable} An Observable that takes a source of Observables and propagates the first observable
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* exclusively until it completes before subscribing to the next.
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* @method exhaust
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* @owner Observable
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*/
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export function exhaust() {
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return (source) => source.lift(new SwitchFirstOperator());
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}
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class SwitchFirstOperator {
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call(subscriber, source) {
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return source.subscribe(new SwitchFirstSubscriber(subscriber));
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}
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}
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/**
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* We need this JSDoc comment for affecting ESDoc.
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* @ignore
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* @extends {Ignored}
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*/
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class SwitchFirstSubscriber extends OuterSubscriber {
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constructor(destination) {
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super(destination);
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this.hasCompleted = false;
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this.hasSubscription = false;
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}
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_next(value) {
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if (!this.hasSubscription) {
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this.hasSubscription = true;
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this.add(subscribeToResult(this, value));
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}
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}
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_complete() {
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this.hasCompleted = true;
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if (!this.hasSubscription) {
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this.destination.complete();
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}
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}
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notifyComplete(innerSub) {
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this.remove(innerSub);
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this.hasSubscription = false;
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if (this.hasCompleted) {
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this.destination.complete();
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}
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}
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}
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//# sourceMappingURL=exhaust.js.map
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