| import { Operator } from '../Operator'; |
| import { Observable } from '../Observable'; |
| import { Subscriber } from '../Subscriber'; |
| import { Subscription } from '../Subscription'; |
| import { OuterSubscriber } from '../OuterSubscriber'; |
| import { InnerSubscriber } from '../InnerSubscriber'; |
| import { subscribeToResult } from '../util/subscribeToResult'; |
| import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types'; |
| import { map } from './map'; |
| import { from } from '../observable/from'; |
| |
| /* 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> |
| * |
| * ![](switchMap.png) |
| * |
| * 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 OuterSubscriber<T, R> { |
| private index: number = 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, value, index); |
| } |
| |
| private _innerSub(result: ObservableInput<R>, value: T, index: number) { |
| const innerSubscription = this.innerSubscription; |
| if (innerSubscription) { |
| innerSubscription.unsubscribe(); |
| } |
| const innerSubscriber = new InnerSubscriber(this, undefined, undefined); |
| const destination = this.destination as Subscription; |
| destination.add(innerSubscriber); |
| this.innerSubscription = subscribeToResult(this, result, value, index, innerSubscriber); |
| } |
| |
| protected _complete(): void { |
| const {innerSubscription} = this; |
| if (!innerSubscription || innerSubscription.closed) { |
| super._complete(); |
| } |
| this.unsubscribe(); |
| } |
| |
| protected _unsubscribe() { |
| this.innerSubscription = null; |
| } |
| |
| notifyComplete(innerSub: Subscription): void { |
| const destination = this.destination as Subscription; |
| destination.remove(innerSub); |
| this.innerSubscription = null; |
| if (this.isStopped) { |
| super._complete(); |
| } |
| } |
| |
| notifyNext(outerValue: T, innerValue: R, |
| outerIndex: number, innerIndex: number, |
| innerSub: InnerSubscriber<T, R>): void { |
| this.destination.next(innerValue); |
| } |
| } |