es6/operator/sample.js

import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
/**
 * 发出源 Observable 最新发出的值当另一个 `notifier` Observable发送时。
 *
 * <span class="informal">就像是 {@link sampleTime}， 但是无论何时`notifier` Observable
 * 进行了发送都会去取样。</span>
 *
 * <img src="./img/sample.png" width="100%">
 *
 * 无论何时 `notifier` Observable 发出一个值或者完成， `sample` 会去源 Observable 中发送上次
 * 取样后源 Observable 发出的最新值， 除非源在上一次取样后没有发出值。 `notifier`会被订阅只要输出
 * Observable 被订阅。
 *
 * @example <caption>每次点击， 取样最新的 "seconds" 时间器</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 被用来取样的源 Observable。
 * @return {Observable<T>} Observable，该 Observable 发出当通知 Observable
 * 发出值或者完成时从源 Observable 取样的最新值。
 * @method sample
 * @owner Observable
 */
export function sample(notifier) {
    return this.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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