128 lines
4.8 KiB
JavaScript
128 lines
4.8 KiB
JavaScript
import { OuterSubscriber } from '../OuterSubscriber';
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import { subscribeToResult } from '../util/subscribeToResult';
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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 only if the previous projected Observable has completed.
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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 exhaust}.</span>
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*
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* <img src="./img/exhaustMap.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. When it projects a source value to
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* an Observable, the output Observable begins emitting the items emitted by
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* that projected Observable. However, `exhaustMap` ignores every new projected
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* Observable if the previous projected Observable has not yet completed. Once
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* that one completes, it will accept and flatten the next projected Observable
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* and repeat this process.
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*
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* @example <caption>Run a finite timer for each click, only if there is no currently active timer</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var result = clicks.exhaustMap((ev) => Rx.Observable.interval(1000).take(5));
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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 exhaust}
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* @see {@link mergeMap}
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* @see {@link switchMap}
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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 containing projected Observables
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* of each item of the source, ignoring projected Observables that start before
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* their preceding Observable has completed.
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* @method exhaustMap
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* @owner Observable
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*/
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export function exhaustMap(project, resultSelector) {
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return (source) => source.lift(new SwitchFirstMapOperator(project, resultSelector));
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}
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class SwitchFirstMapOperator {
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constructor(project, resultSelector) {
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this.project = project;
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this.resultSelector = resultSelector;
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}
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call(subscriber, source) {
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return source.subscribe(new SwitchFirstMapSubscriber(subscriber, this.project, this.resultSelector));
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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 SwitchFirstMapSubscriber extends OuterSubscriber {
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constructor(destination, project, resultSelector) {
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super(destination);
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this.project = project;
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this.resultSelector = resultSelector;
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this.hasSubscription = false;
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this.hasCompleted = false;
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this.index = 0;
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}
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_next(value) {
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if (!this.hasSubscription) {
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this.tryNext(value);
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}
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}
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tryNext(value) {
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const index = this.index++;
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const destination = this.destination;
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try {
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const result = this.project(value, index);
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this.hasSubscription = true;
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this.add(subscribeToResult(this, result, value, index));
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}
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catch (err) {
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destination.error(err);
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}
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}
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_complete() {
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this.hasCompleted = true;
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if (!this.hasSubscription) {
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this.destination.complete();
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}
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}
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notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
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const { resultSelector, destination } = this;
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if (resultSelector) {
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this.trySelectResult(outerValue, innerValue, outerIndex, innerIndex);
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}
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else {
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destination.next(innerValue);
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}
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}
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trySelectResult(outerValue, innerValue, outerIndex, innerIndex) {
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const { resultSelector, destination } = this;
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try {
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const result = resultSelector(outerValue, innerValue, outerIndex, innerIndex);
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destination.next(result);
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}
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catch (err) {
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destination.error(err);
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}
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}
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notifyError(err) {
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this.destination.error(err);
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}
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notifyComplete(innerSub) {
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this.remove(innerSub);
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this.hasSubscription = false;
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if (this.hasCompleted) {
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this.destination.complete();
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}
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}
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}
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//# sourceMappingURL=exhaustMap.js.map
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