work.suroh.tk/node_modules/rxjs/_esm2015/operators/exhaustMap.js

128 lines
4.8 KiB
JavaScript

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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