| import { Operator } from '../Operator'; |
| import { Observable } from '../Observable'; |
| import { Subscriber } from '../Subscriber'; |
| import { Subscription } from '../Subscription'; |
| import { OuterSubscriber } from '../OuterSubscriber'; |
| import { subscribeToResult } from '../util/subscribeToResult'; |
| import { ObservableInput, OperatorFunction, TeardownLogic } from '../types'; |
| |
| export function exhaust<T>(): OperatorFunction<ObservableInput<T>, T>; |
| export function exhaust<R>(): OperatorFunction<any, R>; |
| |
| /** |
| * Converts a higher-order Observable into a first-order Observable by dropping |
| * inner Observables while the previous inner Observable has not yet completed. |
| * |
| * <span class="informal">Flattens an Observable-of-Observables by dropping the |
| * next inner Observables while the current inner is still executing.</span> |
| * |
| * ![](exhaust.png) |
| * |
| * `exhaust` subscribes to an Observable that emits Observables, also known as a |
| * higher-order Observable. Each time it observes one of these emitted inner |
| * Observables, the output Observable begins emitting the items emitted by that |
| * inner Observable. So far, it behaves like {@link mergeAll}. However, |
| * `exhaust` ignores every new inner Observable if the previous Observable has |
| * not yet completed. Once that one completes, it will accept and flatten the |
| * next inner Observable and repeat this process. |
| * |
| * ## Example |
| * Run a finite timer for each click, only if there is no currently active timer |
| * ```ts |
| * import { fromEvent, interval } from 'rxjs'; |
| * import { exhaust, map, take } from 'rxjs/operators'; |
| * |
| * const clicks = fromEvent(document, 'click'); |
| * const higherOrder = clicks.pipe( |
| * map((ev) => interval(1000).pipe(take(5))), |
| * ); |
| * const result = higherOrder.pipe(exhaust()); |
| * result.subscribe(x => console.log(x)); |
| * ``` |
| * |
| * @see {@link combineAll} |
| * @see {@link concatAll} |
| * @see {@link switchAll} |
| * @see {@link switchMap} |
| * @see {@link mergeAll} |
| * @see {@link exhaustMap} |
| * @see {@link zipAll} |
| * |
| * @return {Observable} An Observable that takes a source of Observables and propagates the first observable |
| * exclusively until it completes before subscribing to the next. |
| * @method exhaust |
| * @owner Observable |
| */ |
| export function exhaust<T>(): OperatorFunction<any, T> { |
| return (source: Observable<T>) => source.lift(new SwitchFirstOperator<T>()); |
| } |
| |
| class SwitchFirstOperator<T> implements Operator<T, T> { |
| call(subscriber: Subscriber<T>, source: any): TeardownLogic { |
| return source.subscribe(new SwitchFirstSubscriber(subscriber)); |
| } |
| } |
| |
| /** |
| * We need this JSDoc comment for affecting ESDoc. |
| * @ignore |
| * @extends {Ignored} |
| */ |
| class SwitchFirstSubscriber<T> extends OuterSubscriber<T, T> { |
| private hasCompleted: boolean = false; |
| private hasSubscription: boolean = false; |
| |
| constructor(destination: Subscriber<T>) { |
| super(destination); |
| } |
| |
| protected _next(value: T): void { |
| if (!this.hasSubscription) { |
| this.hasSubscription = true; |
| this.add(subscribeToResult(this, value)); |
| } |
| } |
| |
| protected _complete(): void { |
| this.hasCompleted = true; |
| if (!this.hasSubscription) { |
| this.destination.complete(); |
| } |
| } |
| |
| notifyComplete(innerSub: Subscription): void { |
| this.remove(innerSub); |
| this.hasSubscription = false; |
| if (this.hasCompleted) { |
| this.destination.complete(); |
| } |
| } |
| } |