es6/operators/sample.js

import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
/**
 * Emits the most recently emitted value from the source Observable whenever
 * another Observable, the `notifier`, emits.
 *
 * <span class="informal">It's like {@link sampleTime}, but samples whenever
 * the `notifier` Observable emits something.</span>
 *
 * <img src="./img/sample.png" width="100%">
 *
 * Whenever the `notifier` Observable emits a value or completes, `sample`
 * looks at the source Observable and emits whichever value it has most recently
 * emitted since the previous sampling, unless the source has not emitted
 * anything since the previous sampling. The `notifier` is subscribed to as soon
 * as the output Observable is subscribed.
 *
 * @example <caption>On every click, sample the most recent "seconds" timer</caption>
 * var seconds = Rx.Observable.interval(1000);
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var result = seconds.sample(clicks);
 * result.subscribe(x => console.log(x));
 *
 * @see {@link audit}
 * @see {@link debounce}
 * @see {@link sampleTime}
 * @see {@link throttle}
 *
 * @param {Observable<any>} notifier The Observable to use for sampling the
 * source Observable.
 * @return {Observable<T>} An Observable that emits the results of sampling the
 * values emitted by the source Observable whenever the notifier Observable
 * emits value or completes.
 * @method sample
 * @owner Observable
 */
export function sample(notifier) {
    return (source) => source.lift(new SampleOperator(notifier));
}
class SampleOperator {
    constructor(notifier) {
        this.notifier = notifier;
    }
    call(subscriber, source) {
        const sampleSubscriber = new SampleSubscriber(subscriber);
        const subscription = source.subscribe(sampleSubscriber);
        subscription.add(subscribeToResult(sampleSubscriber, this.notifier));
        return subscription;
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class SampleSubscriber extends OuterSubscriber {
    constructor() {
        super(...arguments);
        this.hasValue = false;
    }
    _next(value) {
        this.value = value;
        this.hasValue = true;
    }
    notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
        this.emitValue();
    }
    notifyComplete() {
        this.emitValue();
    }
    emitValue() {
        if (this.hasValue) {
            this.hasValue = false;
            this.destination.next(this.value);
        }
    }
}
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