import {Operator} from '../Operator';
import {Observable} from '../Observable';
import {Subscriber} from '../Subscriber';
import {OuterSubscriber} from '../OuterSubscriber';
import {subscribeToResult} from '../util/subscribeToResult';
/**
* Returns an Observable that, when the specified sampler Observable emits an item or completes, it then emits the most
* recently emitted item (if any) emitted by the source Observable since the previous emission from the sampler
* Observable.
*
* <img src="./img/sample.png" width="100%">
*
* @param {Observable} sampler - the Observable to use for sampling the source Observable.
* @returns {Observable<T>} an Observable that emits the results of sampling the items emitted by this Observable
* whenever the sampler Observable emits an item or completes.
*/
export function sample<T>(notifier: Observable<any>): Observable<T> {
return this.lift(new SampleOperator(notifier));
}
class SampleOperator<T> implements Operator<T, T> {
constructor(private notifier: Observable<any>) {
}
call(subscriber: Subscriber<T>) {
return new SampleSubscriber(subscriber, this.notifier);
}
}
class SampleSubscriber<T, R> extends OuterSubscriber<T, R> {
private value: T;
private hasValue: boolean = false;
constructor(destination: Subscriber<any>, notifier: Observable<any>) {
super(destination);
this.add(subscribeToResult(this, notifier));
}
protected _next(value: T) {
this.value = value;
this.hasValue = true;
}
notifyNext(outerValue: T, innerValue: R, outerIndex: number, innerIndex: number): void {
this.emitValue();
}
notifyComplete(): void {
this.emitValue();
}
emitValue() {
if (this.hasValue) {
this.hasValue = false;
this.destination.next(this.value);
}
}
}
|