exhaust.js

/** PURE_IMPORTS_START .._OuterSubscriber,.._util_subscribeToResult PURE_IMPORTS_END */
var __extends = (this && this.__extends) || function (d, b) {
    for (var p in b)
        if (b.hasOwnProperty(p))
            d[p] = b[p];
    function __() { this.constructor = d; }
    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};
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 function (source) { return source.lift(new SwitchFirstOperator()); };
}
var SwitchFirstOperator = /*@__PURE__*/ (/*@__PURE__*/ function () {
    function SwitchFirstOperator() {
    }
    SwitchFirstOperator.prototype.call = function (subscriber, source) {
        return source.subscribe(new SwitchFirstSubscriber(subscriber));
    };
    return SwitchFirstOperator;
}());
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
var SwitchFirstSubscriber = /*@__PURE__*/ (/*@__PURE__*/ function (_super) {
    __extends(SwitchFirstSubscriber, _super);
    function SwitchFirstSubscriber(destination) {
        _super.call(this, destination);
        this.hasCompleted = false;
        this.hasSubscription = false;
    }
    SwitchFirstSubscriber.prototype._next = function (value) {
        if (!this.hasSubscription) {
            this.hasSubscription = true;
            this.add(subscribeToResult(this, value));
        }
    };
    SwitchFirstSubscriber.prototype._complete = function () {
        this.hasCompleted = true;
        if (!this.hasSubscription) {
            this.destination.complete();
        }
    };
    SwitchFirstSubscriber.prototype.notifyComplete = function (innerSub) {
        this.remove(innerSub);
        this.hasSubscription = false;
        if (this.hasCompleted) {
            this.destination.complete();
        }
    };
    return SwitchFirstSubscriber;
}(OuterSubscriber));
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