es6/operator/windowWhen.js

import { Subject } from '../Subject';
import { tryCatch } from '../util/tryCatch';
import { errorObject } from '../util/errorObject';
import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
/**
 * 将源 Observable 的值分支成嵌套的 Observable ，通过使用关闭 Observable 的工厂函数来决定何时开启新的窗口。
 *
 * <span class="informal">就像是 {@link bufferWhen}, 但是发出的是嵌套的 Observable
 * 而不是数组。</span>
 *
 * <img src="./img/windowWhen.png" width="100%">
 *
 * 返回的 Observable 发出从源 Observable 收集到的项的窗口。 输出 Observable 发出连接的，非重叠的窗口。
 * 每当由指定的 closingSelector 函数产生的 Observable 发出项，它会发出当前窗口并开启一个新窗口。
 * 当输出 Observable 被订阅的时候立马开启第一个窗口。
 *
 * @example <caption>在每个秒速随机(1-5秒)的窗口中，只发出最开始的两次点击事件</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var result = clicks
 *   .windowWhen(() => Rx.Observable.interval(1000 + Math.random() * 4000))
 *   .map(win => win.take(2)) // 每个窗口最多两个发送
 *   .mergeAll(); // 打平高阶Observable
 * result.subscribe(x => console.log(x));
 *
 * @see {@link window}
 * @see {@link windowCount}
 * @see {@link windowTime}
 * @see {@link windowToggle}
 * @see {@link bufferWhen}
 *
 * @param {function(): Observable} closingSelector 函数，不接受参数并且返回 Observable，
 * 该 Observable 发出信号(`next` 或者 `complete`)以决定何时关闭前一个窗口，开启新一个窗口。
 * @return {Observable<Observable<T>>} 窗口的 Observable，每个窗口又是值的 Observable(译者注：其实就是高阶 Observable )。
 * @method windowWhen
 * @owner Observable
 */
export function windowWhen(closingSelector) {
    return this.lift(new WindowOperator(closingSelector));
}
class WindowOperator {
    constructor(closingSelector) {
        this.closingSelector = closingSelector;
    }
    call(subscriber, source) {
        return source.subscribe(new WindowSubscriber(subscriber, this.closingSelector));
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class WindowSubscriber extends OuterSubscriber {
    constructor(destination, closingSelector) {
        super(destination);
        this.destination = destination;
        this.closingSelector = closingSelector;
        this.openWindow();
    }
    notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
        this.openWindow(innerSub);
    }
    notifyError(error, innerSub) {
        this._error(error);
    }
    notifyComplete(innerSub) {
        this.openWindow(innerSub);
    }
    _next(value) {
        this.window.next(value);
    }
    _error(err) {
        this.window.error(err);
        this.destination.error(err);
        this.unsubscribeClosingNotification();
    }
    _complete() {
        this.window.complete();
        this.destination.complete();
        this.unsubscribeClosingNotification();
    }
    unsubscribeClosingNotification() {
        if (this.closingNotification) {
            this.closingNotification.unsubscribe();
        }
    }
    openWindow(innerSub = null) {
        if (innerSub) {
            this.remove(innerSub);
            innerSub.unsubscribe();
        }
        const prevWindow = this.window;
        if (prevWindow) {
            prevWindow.complete();
        }
        const window = this.window = new Subject();
        this.destination.next(window);
        const closingNotifier = tryCatch(this.closingSelector)();
        if (closingNotifier === errorObject) {
            const err = errorObject.e;
            this.destination.error(err);
            this.window.error(err);
        }
        else {
            this.add(this.closingNotification = subscribeToResult(this, closingNotifier));
        }
    }
}
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