es6/operator/sampleTime.js

import { Subscriber } from '../Subscriber';
import { async } from '../scheduler/async';
/**
 * 在周期时间间隔内发出源 Observable 发出的最新值。
 *
 * <span class="informal">在周期时间间隔内取样源 Observable ， 发出取样的。</span>
 *
 * <img src="./img/sampleTime.png" width="100%">
 *
 * `sampleTime` 周期性的查看源 Observable 并且发出上次取样后发出的最新的值， 除非上次取样后
 * 就没有再发出数据了。 取样在每个周期毫秒(或者时间单位由可选的调度器参数决定)内定期发生。 只要
 * 输出 Observable 被订阅取样就开始。
 *
 * @example <caption>每秒， 发出最近的一个点击</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var result = clicks.sampleTime(1000);
 * result.subscribe(x => console.log(x));
 *
 * @see {@link auditTime}
 * @see {@link debounceTime}
 * @see {@link delay}
 * @see {@link sample}
 * @see {@link throttleTime}
 *
 * @param {number} period 用毫秒或者由可选的调度器参数决定的时间单位表示的取样周期。
 * @param {Scheduler} [scheduler=async] {@link IScheduler}用来管理取样的时间。
 * @return {Observable<T>} Observable，该 Observable 发出特定的时间周期从源 Observable
 * 取样的最新值。
 * @method sampleTime
 * @owner Observable
 */
export function sampleTime(period, scheduler = async) {
    return this.lift(new SampleTimeOperator(period, scheduler));
}
class SampleTimeOperator {
    constructor(period, scheduler) {
        this.period = period;
        this.scheduler = scheduler;
    }
    call(subscriber, source) {
        return source.subscribe(new SampleTimeSubscriber(subscriber, this.period, this.scheduler));
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class SampleTimeSubscriber extends Subscriber {
    constructor(destination, period, scheduler) {
        super(destination);
        this.period = period;
        this.scheduler = scheduler;
        this.hasValue = false;
        this.add(scheduler.schedule(dispatchNotification, period, { subscriber: this, period }));
    }
    _next(value) {
        this.lastValue = value;
        this.hasValue = true;
    }
    notifyNext() {
        if (this.hasValue) {
            this.hasValue = false;
            this.destination.next(this.lastValue);
        }
    }
}
function dispatchNotification(state) {
    let { subscriber, period } = state;
    subscriber.notifyNext();
    this.schedule(state, period);
}
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