187 lines
7.7 KiB
JavaScript
187 lines
7.7 KiB
JavaScript
import { Observable } from '../Observable';
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import { EmptyObservable } from './EmptyObservable';
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import { isArray } from '../util/isArray';
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import { subscribeToResult } from '../util/subscribeToResult';
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import { OuterSubscriber } from '../OuterSubscriber';
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/**
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* We need this JSDoc comment for affecting ESDoc.
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* @extends {Ignored}
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* @hide true
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*/
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export class ForkJoinObservable extends Observable {
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constructor(sources, resultSelector) {
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super();
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this.sources = sources;
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this.resultSelector = resultSelector;
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}
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/* tslint:enable:max-line-length */
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/**
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* Joins last values emitted by passed Observables.
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*
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* <span class="informal">Wait for Observables to complete and then combine last values they emitted.</span>
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*
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* <img src="./img/forkJoin.png" width="100%">
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*
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* `forkJoin` is an operator that takes any number of Observables which can be passed either as an array
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* or directly as arguments. If no input Observables are provided, resulting stream will complete
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* immediately.
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*
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* `forkJoin` will wait for all passed Observables to complete and then it will emit an array with last
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* values from corresponding Observables. So if you pass `n` Observables to the operator, resulting
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* array will have `n` values, where first value is the last thing emitted by the first Observable,
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* second value is the last thing emitted by the second Observable and so on. That means `forkJoin` will
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* not emit more than once and it will complete after that. If you need to emit combined values not only
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* at the end of lifecycle of passed Observables, but also throughout it, try out {@link combineLatest}
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* or {@link zip} instead.
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*
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* In order for resulting array to have the same length as the number of input Observables, whenever any of
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* that Observables completes without emitting any value, `forkJoin` will complete at that moment as well
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* and it will not emit anything either, even if it already has some last values from other Observables.
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* Conversely, if there is an Observable that never completes, `forkJoin` will never complete as well,
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* unless at any point some other Observable completes without emitting value, which brings us back to
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* the previous case. Overall, in order for `forkJoin` to emit a value, all Observables passed as arguments
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* have to emit something at least once and complete.
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*
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* If any input Observable errors at some point, `forkJoin` will error as well and all other Observables
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* will be immediately unsubscribed.
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*
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* Optionally `forkJoin` accepts project function, that will be called with values which normally
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* would land in emitted array. Whatever is returned by project function, will appear in output
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* Observable instead. This means that default project can be thought of as a function that takes
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* all its arguments and puts them into an array. Note that project function will be called only
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* when output Observable is supposed to emit a result.
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*
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* @example <caption>Use forkJoin with operator emitting immediately</caption>
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* const observable = Rx.Observable.forkJoin(
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* Rx.Observable.of(1, 2, 3, 4),
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* Rx.Observable.of(5, 6, 7, 8)
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* );
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* observable.subscribe(
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* value => console.log(value),
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* err => {},
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* () => console.log('This is how it ends!')
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* );
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*
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* // Logs:
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* // [4, 8]
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* // "This is how it ends!"
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*
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*
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* @example <caption>Use forkJoin with operator emitting after some time</caption>
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* const observable = Rx.Observable.forkJoin(
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* Rx.Observable.interval(1000).take(3), // emit 0, 1, 2 every second and complete
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* Rx.Observable.interval(500).take(4) // emit 0, 1, 2, 3 every half a second and complete
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* );
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* observable.subscribe(
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* value => console.log(value),
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* err => {},
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* () => console.log('This is how it ends!')
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* );
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*
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* // Logs:
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* // [2, 3] after 3 seconds
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* // "This is how it ends!" immediately after
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*
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*
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* @example <caption>Use forkJoin with project function</caption>
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* const observable = Rx.Observable.forkJoin(
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* Rx.Observable.interval(1000).take(3), // emit 0, 1, 2 every second and complete
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* Rx.Observable.interval(500).take(4), // emit 0, 1, 2, 3 every half a second and complete
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* (n, m) => n + m
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* );
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* observable.subscribe(
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* value => console.log(value),
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* err => {},
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* () => console.log('This is how it ends!')
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* );
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*
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* // Logs:
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* // 5 after 3 seconds
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* // "This is how it ends!" immediately after
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*
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* @see {@link combineLatest}
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* @see {@link zip}
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*
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* @param {...SubscribableOrPromise} sources Any number of Observables provided either as an array or as an arguments
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* passed directly to the operator.
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* @param {function} [project] Function that takes values emitted by input Observables and returns value
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* that will appear in resulting Observable instead of default array.
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* @return {Observable} Observable emitting either an array of last values emitted by passed Observables
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* or value from project function.
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* @static true
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* @name forkJoin
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* @owner Observable
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*/
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static create(...sources) {
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if (sources === null || arguments.length === 0) {
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return new EmptyObservable();
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}
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let resultSelector = null;
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if (typeof sources[sources.length - 1] === 'function') {
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resultSelector = sources.pop();
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}
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// if the first and only other argument besides the resultSelector is an array
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// assume it's been called with `forkJoin([obs1, obs2, obs3], resultSelector)`
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if (sources.length === 1 && isArray(sources[0])) {
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sources = sources[0];
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}
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if (sources.length === 0) {
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return new EmptyObservable();
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}
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return new ForkJoinObservable(sources, resultSelector);
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}
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/** @deprecated internal use only */ _subscribe(subscriber) {
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return new ForkJoinSubscriber(subscriber, this.sources, this.resultSelector);
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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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class ForkJoinSubscriber extends OuterSubscriber {
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constructor(destination, sources, resultSelector) {
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super(destination);
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this.sources = sources;
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this.resultSelector = resultSelector;
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this.completed = 0;
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this.haveValues = 0;
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const len = sources.length;
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this.total = len;
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this.values = new Array(len);
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for (let i = 0; i < len; i++) {
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const source = sources[i];
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const innerSubscription = subscribeToResult(this, source, null, i);
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if (innerSubscription) {
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innerSubscription.outerIndex = i;
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this.add(innerSubscription);
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}
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}
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}
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notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
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this.values[outerIndex] = innerValue;
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if (!innerSub._hasValue) {
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innerSub._hasValue = true;
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this.haveValues++;
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}
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}
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notifyComplete(innerSub) {
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const destination = this.destination;
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const { haveValues, resultSelector, values } = this;
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const len = values.length;
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if (!innerSub._hasValue) {
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destination.complete();
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return;
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}
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this.completed++;
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if (this.completed !== len) {
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return;
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}
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if (haveValues === len) {
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const value = resultSelector ? resultSelector.apply(this, values) : values;
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destination.next(value);
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}
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destination.complete();
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}
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}
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//# sourceMappingURL=ForkJoinObservable.js.map
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