import { Operator } from '../Operator';
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import { Observable } from '../Observable';
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import { Subscriber } from '../Subscriber';
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import { MonoTypeOperatorFunction, TeardownLogic } from '../types';
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import { SimpleOuterSubscriber, innerSubscribe, SimpleInnerSubscriber } from '../innerSubscribe';
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/**
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* Emits the most recently emitted value from the source Observable whenever
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* another Observable, the `notifier`, emits.
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*
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* <span class="informal">It's like {@link sampleTime}, but samples whenever
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* the `notifier` Observable emits something.</span>
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*
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* 
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*
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* Whenever the `notifier` Observable emits a value or completes, `sample`
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* looks at the source Observable and emits whichever value it has most recently
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* emitted since the previous sampling, unless the source has not emitted
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* anything since the previous sampling. The `notifier` is subscribed to as soon
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* as the output Observable is subscribed.
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*
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* ## Example
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* On every click, sample the most recent "seconds" timer
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* ```ts
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* import { fromEvent, interval } from 'rxjs';
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* import { sample } from 'rxjs/operators';
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*
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* const seconds = interval(1000);
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* const clicks = fromEvent(document, 'click');
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* const result = seconds.pipe(sample(clicks));
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* result.subscribe(x => console.log(x));
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* ```
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*
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* @see {@link audit}
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* @see {@link debounce}
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* @see {@link sampleTime}
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* @see {@link throttle}
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*
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* @param {Observable<any>} notifier The Observable to use for sampling the
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* source Observable.
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* @return {Observable<T>} An Observable that emits the results of sampling the
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* values emitted by the source Observable whenever the notifier Observable
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* emits value or completes.
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* @method sample
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* @owner Observable
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*/
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export function sample<T>(notifier: Observable<any>): MonoTypeOperatorFunction<T> {
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return (source: Observable<T>) => source.lift(new SampleOperator(notifier));
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}
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class SampleOperator<T> implements Operator<T, T> {
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constructor(private notifier: Observable<any>) {
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}
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call(subscriber: Subscriber<T>, source: any): TeardownLogic {
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const sampleSubscriber = new SampleSubscriber(subscriber);
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const subscription = source.subscribe(sampleSubscriber);
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subscription.add(innerSubscribe(this.notifier, new SimpleInnerSubscriber(sampleSubscriber)));
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return subscription;
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}
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}
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/**
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* We need this JSDoc comment for affecting ESDoc.
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* @ignore
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* @extends {Ignored}
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*/
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class SampleSubscriber<T, R> extends SimpleOuterSubscriber<T, R> {
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private value?: T;
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private hasValue: boolean = false;
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protected _next(value: T) {
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this.value = value;
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this.hasValue = true;
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}
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notifyNext(): void {
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this.emitValue();
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}
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notifyComplete(): void {
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this.emitValue();
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}
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emitValue() {
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if (this.hasValue) {
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this.hasValue = false;
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this.destination.next!(this.value!);
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}
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}
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}
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