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- import { Operator } from '../Operator';
- import { Observable } from '../Observable';
- import { Subscriber } from '../Subscriber';
- import { Subscription } from '../Subscription';
- import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types';
- import { map } from './map';
- import { from } from '../observable/from';
- import { SimpleOuterSubscriber, SimpleInnerSubscriber, innerSubscribe } from '../innerSubscribe';
- /* tslint:disable:max-line-length */
- export function switchMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O): OperatorFunction<T, ObservedValueOf<O>>;
- /** @deprecated resultSelector is no longer supported, use inner map instead */
- export function switchMap<T, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: undefined): OperatorFunction<T, ObservedValueOf<O>>;
- /** @deprecated resultSelector is no longer supported, use inner map instead */
- export function switchMap<T, R, O extends ObservableInput<any>>(project: (value: T, index: number) => O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
- /* tslint:enable:max-line-length */
- /**
- * Projects each source value to an Observable which is merged in the output
- * Observable, emitting values only from the most recently projected Observable.
- *
- * <span class="informal">Maps each value to an Observable, then flattens all of
- * these inner Observables.</span>
- *
- * 
- *
- * Returns an Observable that emits items based on applying a function that you
- * supply to each item emitted by the source Observable, where that function
- * returns an (so-called "inner") Observable. Each time it observes one of these
- * inner Observables, the output Observable begins emitting the items emitted by
- * that inner Observable. When a new inner Observable is emitted, `switchMap`
- * stops emitting items from the earlier-emitted inner Observable and begins
- * emitting items from the new one. It continues to behave like this for
- * subsequent inner Observables.
- *
- * ## Example
- * Generate new Observable according to source Observable values
- * ```typescript
- * import { of } from 'rxjs';
- * import { switchMap } from 'rxjs/operators';
- *
- * const switched = of(1, 2, 3).pipe(switchMap((x: number) => of(x, x ** 2, x ** 3)));
- * switched.subscribe(x => console.log(x));
- * // outputs
- * // 1
- * // 1
- * // 1
- * // 2
- * // 4
- * // 8
- * // ... and so on
- * ```
- *
- * Rerun an interval Observable on every click event
- * ```ts
- * import { fromEvent, interval } from 'rxjs';
- * import { switchMap } from 'rxjs/operators';
- *
- * const clicks = fromEvent(document, 'click');
- * const result = clicks.pipe(switchMap((ev) => interval(1000)));
- * result.subscribe(x => console.log(x));
- * ```
- *
- * @see {@link concatMap}
- * @see {@link exhaustMap}
- * @see {@link mergeMap}
- * @see {@link switchAll}
- * @see {@link switchMapTo}
- *
- * @param {function(value: T, ?index: number): ObservableInput} project A function
- * that, when applied to an item emitted by the source Observable, returns an
- * Observable.
- * @return {Observable} An Observable that emits the result of applying the
- * projection function (and the optional deprecated `resultSelector`) to each item
- * emitted by the source Observable and taking only the values from the most recently
- * projected inner Observable.
- * @method switchMap
- * @owner Observable
- */
- export function switchMap<T, R, O extends ObservableInput<any>>(
- project: (value: T, index: number) => O,
- resultSelector?: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R,
- ): OperatorFunction<T, ObservedValueOf<O>|R> {
- if (typeof resultSelector === 'function') {
- return (source: Observable<T>) => source.pipe(
- switchMap((a, i) => from(project(a, i)).pipe(
- map((b, ii) => resultSelector(a, b, i, ii))
- ))
- );
- }
- return (source: Observable<T>) => source.lift(new SwitchMapOperator(project));
- }
- class SwitchMapOperator<T, R> implements Operator<T, R> {
- constructor(private project: (value: T, index: number) => ObservableInput<R>) {
- }
- call(subscriber: Subscriber<R>, source: any): any {
- return source.subscribe(new SwitchMapSubscriber(subscriber, this.project));
- }
- }
- /**
- * We need this JSDoc comment for affecting ESDoc.
- * @ignore
- * @extends {Ignored}
- */
- class SwitchMapSubscriber<T, R> extends SimpleOuterSubscriber<T, R> {
- private index = 0;
- private innerSubscription?: Subscription;
- constructor(destination: Subscriber<R>,
- private project: (value: T, index: number) => ObservableInput<R>) {
- super(destination);
- }
- protected _next(value: T) {
- let result: ObservableInput<R>;
- const index = this.index++;
- try {
- result = this.project(value, index);
- } catch (error) {
- this.destination.error!(error);
- return;
- }
- this._innerSub(result);
- }
- private _innerSub(result: ObservableInput<R>) {
- const innerSubscription = this.innerSubscription;
- if (innerSubscription) {
- innerSubscription.unsubscribe();
- }
- const innerSubscriber = new SimpleInnerSubscriber(this);
- const destination = this.destination as Subscription;
- destination.add(innerSubscriber);
- this.innerSubscription = innerSubscribe(result, innerSubscriber);
- // The returned subscription will usually be the subscriber that was
- // passed. However, interop subscribers will be wrapped and for
- // unsubscriptions to chain correctly, the wrapper needs to be added, too.
- if (this.innerSubscription !== innerSubscriber) {
- destination.add(this.innerSubscription);
- }
- }
- protected _complete(): void {
- const {innerSubscription} = this;
- if (!innerSubscription || innerSubscription.closed) {
- super._complete();
- }
- this.unsubscribe();
- }
- protected _unsubscribe() {
- this.innerSubscription = undefined;
- }
- notifyComplete(): void {
- this.innerSubscription = undefined;
- if (this.isStopped) {
- super._complete();
- }
- }
- notifyNext(innerValue: R): void {
- this.destination.next!(innerValue);
- }
- }
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