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