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import { Operator } from '../Operator';
import { Observable } from '../Observable';
import { Subscriber } from '../Subscriber';
import { OperatorFunction, MonoTypeOperatorFunction } from '../types';
/* tslint:disable:max-line-length */
export function defaultIfEmpty<T>(defaultValue?: T): MonoTypeOperatorFunction<T>;
export function defaultIfEmpty<T, R>(defaultValue?: R): OperatorFunction<T, T | R>;
/* tslint:enable:max-line-length */
/**
* Emits a given value if the source Observable completes without emitting any
* `next` value, otherwise mirrors the source Observable.
*
* <span class="informal">If the source Observable turns out to be empty, then
* this operator will emit a default value.</span>
*
* 
*
* `defaultIfEmpty` emits the values emitted by the source Observable or a
* specified default value if the source Observable is empty (completes without
* having emitted any `next` value).
*
* ## Example
* If no clicks happen in 5 seconds, then emit "no clicks"
* ```javascript
* import { fromEvent } from 'rxjs';
* import { defaultIfEmpty, takeUntil } from 'rxjs/operators';
*
* const clicks = fromEvent(document, 'click');
* const clicksBeforeFive = clicks.pipe(takeUntil(interval(5000)));
* const result = clicksBeforeFive.pipe(defaultIfEmpty('no clicks'));
* result.subscribe(x => console.log(x));
* ```
*
* @see {@link empty}
* @see {@link last}
*
* @param {any} [defaultValue=null] The default value used if the source
* Observable is empty.
* @return {Observable} An Observable that emits either the specified
* `defaultValue` if the source Observable emits no items, or the values emitted
* by the source Observable.
* @method defaultIfEmpty
* @owner Observable
*/
export function defaultIfEmpty<T, R>(defaultValue: R = null): OperatorFunction<T, T | R> {
return (source: Observable<T>) => source.lift(new DefaultIfEmptyOperator(defaultValue)) as Observable<T | R>;
}
class DefaultIfEmptyOperator<T, R> implements Operator<T, T | R> {
constructor(private defaultValue: R) {
}
call(subscriber: Subscriber<T | R>, source: any): any {
return source.subscribe(new DefaultIfEmptySubscriber(subscriber, this.defaultValue));
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
class DefaultIfEmptySubscriber<T, R> extends Subscriber<T> {
private isEmpty: boolean = true;
constructor(destination: Subscriber<T | R>, private defaultValue: R) {
super(destination);
}
protected _next(value: T): void {
this.isEmpty = false;
this.destination.next(value);
}
protected _complete(): void {
if (this.isEmpty) {
this.destination.next(this.defaultValue);
}
this.destination.complete();
}
}
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