work.suroh.tk/node_modules/rxjs/_esm2015/operators/exhaust.js

77 lines
2.7 KiB
JavaScript

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