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

118 lines
4.3 KiB
JavaScript

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