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

137 lines
5.1 KiB
JavaScript

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