blob: d0a8daf021bbe543446b927a7ff1e1b51b87e9ae [file] [log] [blame]
import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
/* 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 using {@link switch}.</span>
*
* <img src="./img/switchMap.png" width="100%">
*
* 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 <caption>Rerun an interval Observable on every click event</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var result = clicks.switchMap((ev) => Rx.Observable.interval(1000));
* result.subscribe(x => console.log(x));
*
* @see {@link concatMap}
* @see {@link exhaustMap}
* @see {@link mergeMap}
* @see {@link switch}
* @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.
* @param {function(outerValue: T, innerValue: I, outerIndex: number, innerIndex: number): any} [resultSelector]
* A function to produce the value on the output Observable based on the values
* and the indices of the source (outer) emission and the inner Observable
* emission. The arguments passed to this function are:
* - `outerValue`: the value that came from the source
* - `innerValue`: the value that came from the projected Observable
* - `outerIndex`: the "index" of the value that came from the source
* - `innerIndex`: the "index" of the value from the projected Observable
* @return {Observable} An Observable that emits the result of applying the
* projection function (and the optional `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(project, resultSelector) {
return function switchMapOperatorFunction(source) {
return source.lift(new SwitchMapOperator(project, resultSelector));
};
}
class SwitchMapOperator {
constructor(project, resultSelector) {
this.project = project;
this.resultSelector = resultSelector;
}
call(subscriber, source) {
return source.subscribe(new SwitchMapSubscriber(subscriber, this.project, this.resultSelector));
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
class SwitchMapSubscriber extends OuterSubscriber {
constructor(destination, project, resultSelector) {
super(destination);
this.project = project;
this.resultSelector = resultSelector;
this.index = 0;
}
_next(value) {
let result;
const index = this.index++;
try {
result = this.project(value, index);
}
catch (error) {
this.destination.error(error);
return;
}
this._innerSub(result, value, index);
}
_innerSub(result, value, index) {
const innerSubscription = this.innerSubscription;
if (innerSubscription) {
innerSubscription.unsubscribe();
}
this.add(this.innerSubscription = subscribeToResult(this, result, value, index));
}
_complete() {
const { innerSubscription } = this;
if (!innerSubscription || innerSubscription.closed) {
super._complete();
}
}
_unsubscribe() {
this.innerSubscription = null;
}
notifyComplete(innerSub) {
this.remove(innerSub);
this.innerSubscription = null;
if (this.isStopped) {
super._complete();
}
}
notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
if (this.resultSelector) {
this._tryNotifyNext(outerValue, innerValue, outerIndex, innerIndex);
}
else {
this.destination.next(innerValue);
}
}
_tryNotifyNext(outerValue, innerValue, outerIndex, innerIndex) {
let result;
try {
result = this.resultSelector(outerValue, innerValue, outerIndex, innerIndex);
}
catch (err) {
this.destination.error(err);
return;
}
this.destination.next(result);
}
}
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