102 lines
3.8 KiB
Plaintext
102 lines
3.8 KiB
Plaintext
import { Operator } from '../Operator';
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import { Subscriber } from '../Subscriber';
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import { Observable } from '../Observable';
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import { MonoTypeOperatorFunction, TeardownLogic, ObservableInput } from '../types';
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import { Subscription } from '../Subscription';
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import { SimpleOuterSubscriber, SimpleInnerSubscriber, innerSubscribe } from '../innerSubscribe';
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/**
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* Returns an Observable that skips items emitted by the source Observable until a second Observable emits an item.
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*
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* The `skipUntil` operator causes the observable stream to skip the emission of values until the passed in observable emits the first value.
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* This can be particularly useful in combination with user interactions, responses of http requests or waiting for specific times to pass by.
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*
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* 
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*
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* Internally the `skipUntil` operator subscribes to the passed in observable (in the following called *notifier*) in order to recognize the emission
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* of its first value. When this happens, the operator unsubscribes from the *notifier* and starts emitting the values of the *source*
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* observable. It will never let the *source* observable emit any values if the *notifier* completes or throws an error without emitting
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* a value before.
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*
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* ## Example
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*
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* In the following example, all emitted values of the interval observable are skipped until the user clicks anywhere within the page.
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*
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* ```ts
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* import { interval, fromEvent } from 'rxjs';
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* import { skipUntil } from 'rxjs/operators';
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*
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* const intervalObservable = interval(1000);
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* const click = fromEvent(document, 'click');
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*
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* const emitAfterClick = intervalObservable.pipe(
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* skipUntil(click)
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* );
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* // clicked at 4.6s. output: 5...6...7...8........ or
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* // clicked at 7.3s. output: 8...9...10..11.......
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* const subscribe = emitAfterClick.subscribe(value => console.log(value));
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* ```
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*
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* @param {Observable} notifier - The second Observable that has to emit an item before the source Observable's elements begin to
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* be mirrored by the resulting Observable.
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* @return {Observable<T>} An Observable that skips items from the source Observable until the second Observable emits
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* an item, then emits the remaining items.
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* @method skipUntil
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* @owner Observable
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*/
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export function skipUntil<T>(notifier: Observable<any>): MonoTypeOperatorFunction<T> {
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return (source: Observable<T>) => source.lift(new SkipUntilOperator(notifier));
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}
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class SkipUntilOperator<T> implements Operator<T, T> {
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constructor(private notifier: Observable<any>) {
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}
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call(destination: Subscriber<T>, source: any): TeardownLogic {
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return source.subscribe(new SkipUntilSubscriber(destination, this.notifier));
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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 SkipUntilSubscriber<T, R> extends SimpleOuterSubscriber<T, R> {
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private hasValue: boolean = false;
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private innerSubscription?: Subscription;
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constructor(destination: Subscriber<R>, notifier: ObservableInput<any>) {
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super(destination);
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const innerSubscriber = new SimpleInnerSubscriber(this);
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this.add(innerSubscriber);
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this.innerSubscription = innerSubscriber;
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const innerSubscription = innerSubscribe(notifier, innerSubscriber);
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// The returned subscription will usually be the subscriber that was
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// passed. However, interop subscribers will be wrapped and for
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// unsubscriptions to chain correctly, the wrapper needs to be added, too.
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if (innerSubscription !== innerSubscriber) {
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this.add(innerSubscription);
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this.innerSubscription = innerSubscription;
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}
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}
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protected _next(value: T) {
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if (this.hasValue) {
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super._next(value);
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}
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}
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notifyNext(): void {
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this.hasValue = true;
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if (this.innerSubscription) {
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this.innerSubscription.unsubscribe();
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}
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}
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notifyComplete() {
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/* do nothing */
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}
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}
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