137 lines
5.1 KiB
JavaScript
137 lines
5.1 KiB
JavaScript
import { tryCatch } from '../util/tryCatch';
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import { errorObject } from '../util/errorObject';
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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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* Recursively projects each source value to an Observable which is merged in
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* the output Observable.
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*
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* <span class="informal">It's similar to {@link mergeMap}, but applies the
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* projection function to every source value as well as every output value.
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* It's recursive.</span>
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*
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* <img src="./img/expand.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 Observable, and then merging those resulting Observables and
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* emitting the results of this merger. *Expand* will re-emit on the output
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* Observable every source value. Then, each output value is given to the
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* `project` function which returns an inner Observable to be merged on the
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* output Observable. Those output values resulting from the projection are also
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* given to the `project` function to produce new output values. This is how
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* *expand* behaves recursively.
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*
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* @example <caption>Start emitting the powers of two on every click, at most 10 of them</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var powersOfTwo = clicks
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* .mapTo(1)
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* .expand(x => Rx.Observable.of(2 * x).delay(1000))
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* .take(10);
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* powersOfTwo.subscribe(x => console.log(x));
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*
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* @see {@link mergeMap}
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* @see {@link mergeScan}
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*
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* @param {function(value: T, index: number) => Observable} project A function
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* that, when applied to an item emitted by the source or the output Observable,
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* returns an Observable.
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* @param {number} [concurrent=Number.POSITIVE_INFINITY] Maximum number of input
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* Observables being subscribed to concurrently.
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* @param {Scheduler} [scheduler=null] The IScheduler to use for subscribing to
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* each projected inner Observable.
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* @return {Observable} An Observable that emits the source values and also
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* result of applying the projection function to each value emitted on the
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* output Observable and and merging the results of the Observables obtained
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* from this transformation.
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* @method expand
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* @owner Observable
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*/
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export function expand(project, concurrent = Number.POSITIVE_INFINITY, scheduler = undefined) {
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concurrent = (concurrent || 0) < 1 ? Number.POSITIVE_INFINITY : concurrent;
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return (source) => source.lift(new ExpandOperator(project, concurrent, scheduler));
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}
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export class ExpandOperator {
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constructor(project, concurrent, scheduler) {
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this.project = project;
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this.concurrent = concurrent;
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this.scheduler = scheduler;
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}
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call(subscriber, source) {
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return source.subscribe(new ExpandSubscriber(subscriber, this.project, this.concurrent, this.scheduler));
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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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export class ExpandSubscriber extends OuterSubscriber {
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constructor(destination, project, concurrent, scheduler) {
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super(destination);
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this.project = project;
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this.concurrent = concurrent;
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this.scheduler = scheduler;
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this.index = 0;
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this.active = 0;
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this.hasCompleted = false;
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if (concurrent < Number.POSITIVE_INFINITY) {
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this.buffer = [];
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}
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}
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static dispatch(arg) {
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const { subscriber, result, value, index } = arg;
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subscriber.subscribeToProjection(result, value, index);
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}
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_next(value) {
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const destination = this.destination;
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if (destination.closed) {
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this._complete();
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return;
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}
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const index = this.index++;
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if (this.active < this.concurrent) {
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destination.next(value);
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let result = tryCatch(this.project)(value, index);
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if (result === errorObject) {
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destination.error(errorObject.e);
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}
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else if (!this.scheduler) {
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this.subscribeToProjection(result, value, index);
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}
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else {
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const state = { subscriber: this, result, value, index };
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this.add(this.scheduler.schedule(ExpandSubscriber.dispatch, 0, state));
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}
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}
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else {
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this.buffer.push(value);
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}
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}
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subscribeToProjection(result, value, index) {
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this.active++;
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this.add(subscribeToResult(this, result, value, index));
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}
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_complete() {
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this.hasCompleted = true;
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if (this.hasCompleted && this.active === 0) {
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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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this._next(innerValue);
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}
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notifyComplete(innerSub) {
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const buffer = this.buffer;
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this.remove(innerSub);
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this.active--;
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if (buffer && buffer.length > 0) {
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this._next(buffer.shift());
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}
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if (this.hasCompleted && this.active === 0) {
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this.destination.complete();
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}
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}
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}
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//# sourceMappingURL=expand.js.map
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