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

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2019-12-02 12:22:45 +00:00
import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
/* tslint:enable:max-line-length */
/**
* Projects each source value to the same Observable which is flattened multiple
* times with {@link switch} in the output Observable.
*
* <span class="informal">It's like {@link switchMap}, but maps each value
* always to the same inner Observable.</span>
*
* <img src="./img/switchMapTo.png" width="100%">
*
* Maps each source value to the given Observable `innerObservable` regardless
* of the source value, and then flattens those resulting Observables into one
* single Observable, which is the output Observable. The output Observables
* emits values only from the most recently emitted instance of
* `innerObservable`.
*
* @example <caption>Rerun an interval Observable on every click event</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var result = clicks.switchMapTo(Rx.Observable.interval(1000));
* result.subscribe(x => console.log(x));
*
* @see {@link concatMapTo}
* @see {@link switch}
* @see {@link switchMap}
* @see {@link mergeMapTo}
*
* @param {ObservableInput} innerObservable An Observable to replace each value from
* the source Observable.
* @param {function(outerValue: T, innerValue: I, outerIndex: number, innerIndex: number): any} [resultSelector]
* A function to produce the value on the output Observable based on the values
* and the indices of the source (outer) emission and the inner Observable
* emission. The arguments passed to this function are:
* - `outerValue`: the value that came from the source
* - `innerValue`: the value that came from the projected Observable
* - `outerIndex`: the "index" of the value that came from the source
* - `innerIndex`: the "index" of the value from the projected Observable
* @return {Observable} An Observable that emits items from the given
* `innerObservable` (and optionally transformed through `resultSelector`) every
* time a value is emitted on the source Observable, and taking only the values
* from the most recently projected inner Observable.
* @method switchMapTo
* @owner Observable
*/
export function switchMapTo(innerObservable, resultSelector) {
return (source) => source.lift(new SwitchMapToOperator(innerObservable, resultSelector));
}
class SwitchMapToOperator {
constructor(observable, resultSelector) {
this.observable = observable;
this.resultSelector = resultSelector;
}
call(subscriber, source) {
return source.subscribe(new SwitchMapToSubscriber(subscriber, this.observable, this.resultSelector));
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
class SwitchMapToSubscriber extends OuterSubscriber {
constructor(destination, inner, resultSelector) {
super(destination);
this.inner = inner;
this.resultSelector = resultSelector;
this.index = 0;
}
_next(value) {
const innerSubscription = this.innerSubscription;
if (innerSubscription) {
innerSubscription.unsubscribe();
}
this.add(this.innerSubscription = subscribeToResult(this, this.inner, value, this.index++));
}
_complete() {
const { innerSubscription } = this;
if (!innerSubscription || innerSubscription.closed) {
super._complete();
}
}
/** @deprecated internal use only */ _unsubscribe() {
this.innerSubscription = null;
}
notifyComplete(innerSub) {
this.remove(innerSub);
this.innerSubscription = null;
if (this.isStopped) {
super._complete();
}
}
notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
const { resultSelector, destination } = this;
if (resultSelector) {
this.tryResultSelector(outerValue, innerValue, outerIndex, innerIndex);
}
else {
destination.next(innerValue);
}
}
tryResultSelector(outerValue, innerValue, outerIndex, innerIndex) {
const { resultSelector, destination } = this;
let result;
try {
result = resultSelector(outerValue, innerValue, outerIndex, innerIndex);
}
catch (err) {
destination.error(err);
return;
}
destination.next(result);
}
}
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