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window.ts
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window.ts
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import { Observable } from '../Observable';
import { OperatorFunction, ObservableInput } from '../types';
import { Subject } from '../Subject';
import { operate } from '../util/lift';
import { createOperatorSubscriber } from './OperatorSubscriber';
import { noop } from '../util/noop';
import { innerFrom } from '../observable/innerFrom';
/**
* Branch out the source Observable values as a nested Observable whenever
* `windowBoundaries` emits.
*
* <span class="informal">It's like {@link buffer}, but emits a nested Observable
* instead of an array.</span>
*
* ![](window.png)
*
* Returns an Observable that emits windows of items it collects from the source
* Observable. The output Observable emits connected, non-overlapping
* windows. It emits the current window and opens a new one whenever the
* `windowBoundaries` emits an item. `windowBoundaries` can be any type that
* `ObservableInput` accepts. It internally gets converted to an Observable.
* Because each window is an Observable, the output is a higher-order Observable.
*
* ## Example
*
* In every window of 1 second each, emit at most 2 click events
*
* ```ts
* import { fromEvent, interval, window, map, take, mergeAll } from 'rxjs';
*
* const clicks = fromEvent(document, 'click');
* const sec = interval(1000);
* const result = clicks.pipe(
* window(sec),
* map(win => win.pipe(take(2))), // take at most 2 emissions from each window
* mergeAll() // flatten the Observable-of-Observables
* );
* result.subscribe(x => console.log(x));
* ```
*
* @see {@link windowCount}
* @see {@link windowTime}
* @see {@link windowToggle}
* @see {@link windowWhen}
* @see {@link buffer}
*
* @param windowBoundaries An `ObservableInput` that completes the
* previous window and starts a new window.
* @return A function that returns an Observable of windows, which are
* Observables emitting values of the source Observable.
*/
export function window<T>(windowBoundaries: ObservableInput<any>): OperatorFunction<T, Observable<T>> {
return operate((source, subscriber) => {
let windowSubject: Subject<T> = new Subject<T>();
subscriber.next(windowSubject.asObservable());
const errorHandler = (err: any) => {
windowSubject.error(err);
subscriber.error(err);
};
// Subscribe to our source
source.subscribe(
createOperatorSubscriber(
subscriber,
(value) => windowSubject?.next(value),
() => {
windowSubject.complete();
subscriber.complete();
},
errorHandler
)
);
// Subscribe to the window boundaries.
innerFrom(windowBoundaries).subscribe(
createOperatorSubscriber(
subscriber,
() => {
windowSubject.complete();
subscriber.next((windowSubject = new Subject()));
},
noop,
errorHandler
)
);
return () => {
// Unsubscribing the subject ensures that anyone who has captured
// a reference to this window that tries to use it after it can
// no longer get values from the source will get an ObjectUnsubscribedError.
windowSubject?.unsubscribe();
windowSubject = null!;
};
});
}