53 lines
2.6 KiB
JavaScript
53 lines
2.6 KiB
JavaScript
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import { switchMap as higherOrderSwitchMap } from '../operators/switchMap';
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/* tslint:enable:max-line-length */
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/**
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* Projects each source value to an Observable which is merged in the output
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* Observable, emitting values only from the most recently projected Observable.
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*
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* <span class="informal">Maps each value to an Observable, then flattens all of
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* these inner Observables using {@link switch}.</span>
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*
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* <img src="./img/switchMap.png" width="100%">
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*
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* Returns an Observable that emits items based on applying a function that you
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* supply to each item emitted by the source Observable, where that function
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* returns an (so-called "inner") Observable. Each time it observes one of these
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* inner Observables, the output Observable begins emitting the items emitted by
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* that inner Observable. When a new inner Observable is emitted, `switchMap`
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* stops emitting items from the earlier-emitted inner Observable and begins
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* emitting items from the new one. It continues to behave like this for
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* subsequent inner Observables.
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*
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* @example <caption>Rerun an interval Observable on every click event</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var result = clicks.switchMap((ev) => Rx.Observable.interval(1000));
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* result.subscribe(x => console.log(x));
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*
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* @see {@link concatMap}
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* @see {@link exhaustMap}
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* @see {@link mergeMap}
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* @see {@link switch}
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* @see {@link switchMapTo}
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*
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* @param {function(value: T, ?index: number): ObservableInput} project A function
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* that, when applied to an item emitted by the source Observable, returns an
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* Observable.
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* @param {function(outerValue: T, innerValue: I, outerIndex: number, innerIndex: number): any} [resultSelector]
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* A function to produce the value on the output Observable based on the values
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* and the indices of the source (outer) emission and the inner Observable
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* emission. The arguments passed to this function are:
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* - `outerValue`: the value that came from the source
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* - `innerValue`: the value that came from the projected Observable
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* - `outerIndex`: the "index" of the value that came from the source
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* - `innerIndex`: the "index" of the value from the projected Observable
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* @return {Observable} An Observable that emits the result of applying the
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* projection function (and the optional `resultSelector`) to each item emitted
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* by the source Observable and taking only the values from the most recently
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* projected inner Observable.
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* @method switchMap
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* @owner Observable
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*/
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export function switchMap(project, resultSelector) {
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return higherOrderSwitchMap(project, resultSelector)(this);
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}
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//# sourceMappingURL=switchMap.js.map
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