-
Notifications
You must be signed in to change notification settings - Fork 3k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
feat(expand): add higher-order lettable expand
- Loading branch information
Showing
3 changed files
with
172 additions
and
109 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,169 @@ | ||
| import { Observable } from '../Observable'; | ||
| import { IScheduler } from '../Scheduler'; | ||
| import { Operator } from '../Operator'; | ||
| import { Subscriber } from '../Subscriber'; | ||
| import { tryCatch } from '../util/tryCatch'; | ||
| import { errorObject } from '../util/errorObject'; | ||
| import { Subscription } from '../Subscription'; | ||
| import { OuterSubscriber } from '../OuterSubscriber'; | ||
| import { InnerSubscriber } from '../InnerSubscriber'; | ||
| import { subscribeToResult } from '../util/subscribeToResult'; | ||
| import { MonoTypeOperatorFunction, OperatorFunction } from '../interfaces'; | ||
|
|
||
| /* tslint:disable:max-line-length */ | ||
| export function expand<T>(project: (value: T, index: number) => Observable<T>, concurrent?: number, scheduler?: IScheduler): MonoTypeOperatorFunction<T>; | ||
| export function expand<T, R>(project: (value: T, index: number) => Observable<R>, concurrent?: number, scheduler?: IScheduler): OperatorFunction<T, R>; | ||
| /* 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<T, R>(project: (value: T, index: number) => Observable<R>, | ||
| concurrent: number = Number.POSITIVE_INFINITY, | ||
| scheduler: IScheduler = undefined): OperatorFunction<T, R> { | ||
| concurrent = (concurrent || 0) < 1 ? Number.POSITIVE_INFINITY : concurrent; | ||
|
|
||
| return (source: Observable<T>) => source.lift(new ExpandOperator(project, concurrent, scheduler)); | ||
| } | ||
|
|
||
| export class ExpandOperator<T, R> implements Operator<T, R> { | ||
| constructor(private project: (value: T, index: number) => Observable<R>, | ||
| private concurrent: number, | ||
| private scheduler: IScheduler) { | ||
| } | ||
|
|
||
| call(subscriber: Subscriber<R>, source: any): any { | ||
| return source.subscribe(new ExpandSubscriber(subscriber, this.project, this.concurrent, this.scheduler)); | ||
| } | ||
| } | ||
|
|
||
| interface DispatchArg<T, R> { | ||
| subscriber: ExpandSubscriber<T, R>; | ||
| result: Observable<R>; | ||
| value: any; | ||
| index: number; | ||
| } | ||
|
|
||
| /** | ||
| * We need this JSDoc comment for affecting ESDoc. | ||
| * @ignore | ||
| * @extends {Ignored} | ||
| */ | ||
| export class ExpandSubscriber<T, R> extends OuterSubscriber<T, R> { | ||
| private index: number = 0; | ||
| private active: number = 0; | ||
| private hasCompleted: boolean = false; | ||
| private buffer: any[]; | ||
|
|
||
| constructor(destination: Subscriber<R>, | ||
| private project: (value: T, index: number) => Observable<R>, | ||
| private concurrent: number, | ||
| private scheduler: IScheduler) { | ||
| super(destination); | ||
| if (concurrent < Number.POSITIVE_INFINITY) { | ||
| this.buffer = []; | ||
| } | ||
| } | ||
|
|
||
| private static dispatch<T, R>(arg: DispatchArg<T, R>): void { | ||
| const {subscriber, result, value, index} = arg; | ||
| subscriber.subscribeToProjection(result, value, index); | ||
| } | ||
|
|
||
| protected _next(value: any): void { | ||
| 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: DispatchArg<T, R> = { subscriber: this, result, value, index }; | ||
| this.add(this.scheduler.schedule(ExpandSubscriber.dispatch, 0, state)); | ||
| } | ||
| } else { | ||
| this.buffer.push(value); | ||
| } | ||
| } | ||
|
|
||
| private subscribeToProjection(result: any, value: T, index: number): void { | ||
| this.active++; | ||
| this.add(subscribeToResult<T, R>(this, result, value, index)); | ||
| } | ||
|
|
||
| protected _complete(): void { | ||
| this.hasCompleted = true; | ||
| if (this.hasCompleted && this.active === 0) { | ||
| this.destination.complete(); | ||
| } | ||
| } | ||
|
|
||
| notifyNext(outerValue: T, innerValue: R, | ||
| outerIndex: number, innerIndex: number, | ||
| innerSub: InnerSubscriber<T, R>): void { | ||
| this._next(innerValue); | ||
| } | ||
|
|
||
| notifyComplete(innerSub: Subscription): void { | ||
| 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(); | ||
| } | ||
| } | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters