es6/operators/exhaustMap.js

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