118 lines
4.3 KiB
JavaScript
118 lines
4.3 KiB
JavaScript
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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* Combines the source Observable with other Observables to create an Observable
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* whose values are calculated from the latest values of each, only when the
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* source emits.
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*
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* <span class="informal">Whenever the source Observable emits a value, it
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* computes a formula using that value plus the latest values from other input
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* Observables, then emits the output of that formula.</span>
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*
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* <img src="./img/withLatestFrom.png" width="100%">
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*
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* `withLatestFrom` combines each value from the source Observable (the
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* instance) with the latest values from the other input Observables only when
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* the source emits a value, optionally using a `project` function to determine
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* the value to be emitted on the output Observable. All input Observables must
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* emit at least one value before the output Observable will emit a value.
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*
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* @example <caption>On every click event, emit an array with the latest timer event plus the click event</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var timer = Rx.Observable.interval(1000);
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* var result = clicks.withLatestFrom(timer);
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* result.subscribe(x => console.log(x));
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*
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* @see {@link combineLatest}
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*
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* @param {ObservableInput} other An input Observable to combine with the source
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* Observable. More than one input Observables may be given as argument.
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* @param {Function} [project] Projection function for combining values
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* together. Receives all values in order of the Observables passed, where the
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* first parameter is a value from the source Observable. (e.g.
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* `a.withLatestFrom(b, c, (a1, b1, c1) => a1 + b1 + c1)`). If this is not
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* passed, arrays will be emitted on the output Observable.
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* @return {Observable} An Observable of projected values from the most recent
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* values from each input Observable, or an array of the most recent values from
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* each input Observable.
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* @method withLatestFrom
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* @owner Observable
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*/
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export function withLatestFrom(...args) {
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return (source) => {
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let project;
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if (typeof args[args.length - 1] === 'function') {
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project = args.pop();
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}
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const observables = args;
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return source.lift(new WithLatestFromOperator(observables, project));
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};
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}
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class WithLatestFromOperator {
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constructor(observables, project) {
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this.observables = observables;
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this.project = project;
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}
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call(subscriber, source) {
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return source.subscribe(new WithLatestFromSubscriber(subscriber, this.observables, this.project));
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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 WithLatestFromSubscriber extends OuterSubscriber {
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constructor(destination, observables, project) {
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super(destination);
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this.observables = observables;
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this.project = project;
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this.toRespond = [];
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const len = observables.length;
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this.values = new Array(len);
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for (let i = 0; i < len; i++) {
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this.toRespond.push(i);
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}
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for (let i = 0; i < len; i++) {
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let observable = observables[i];
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this.add(subscribeToResult(this, observable, observable, i));
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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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const toRespond = this.toRespond;
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if (toRespond.length > 0) {
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const found = toRespond.indexOf(outerIndex);
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if (found !== -1) {
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toRespond.splice(found, 1);
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}
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}
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}
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notifyComplete() {
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// noop
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}
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_next(value) {
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if (this.toRespond.length === 0) {
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const args = [value, ...this.values];
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if (this.project) {
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this._tryProject(args);
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}
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else {
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this.destination.next(args);
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}
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}
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}
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_tryProject(args) {
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let result;
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try {
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result = this.project.apply(this, args);
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}
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catch (err) {
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this.destination.error(err);
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return;
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}
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this.destination.next(result);
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}
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}
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//# sourceMappingURL=withLatestFrom.js.map
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