biobulkbende.org/node_modules/rxjs/_esm2015/observable/EmptyObservable.js
2020-09-16 14:23:28 +02:00

72 lines
2.4 KiB
JavaScript

import { Observable } from '../Observable';
/**
* We need this JSDoc comment for affecting ESDoc.
* @extends {Ignored}
* @hide true
*/
export class EmptyObservable extends Observable {
constructor(scheduler) {
super();
this.scheduler = scheduler;
}
/**
* Creates an Observable that emits no items to the Observer and immediately
* emits a complete notification.
*
* <span class="informal">Just emits 'complete', and nothing else.
* </span>
*
* <img src="./img/empty.png" width="100%">
*
* This static operator is useful for creating a simple Observable that only
* emits the complete notification. It can be used for composing with other
* Observables, such as in a {@link mergeMap}.
*
* @example <caption>Emit the number 7, then complete.</caption>
* var result = Rx.Observable.empty().startWith(7);
* result.subscribe(x => console.log(x));
*
* @example <caption>Map and flatten only odd numbers to the sequence 'a', 'b', 'c'</caption>
* var interval = Rx.Observable.interval(1000);
* var result = interval.mergeMap(x =>
* x % 2 === 1 ? Rx.Observable.of('a', 'b', 'c') : Rx.Observable.empty()
* );
* result.subscribe(x => console.log(x));
*
* // Results in the following to the console:
* // x is equal to the count on the interval eg(0,1,2,3,...)
* // x will occur every 1000ms
* // if x % 2 is equal to 1 print abc
* // if x % 2 is not equal to 1 nothing will be output
*
* @see {@link create}
* @see {@link never}
* @see {@link of}
* @see {@link throw}
*
* @param {Scheduler} [scheduler] A {@link IScheduler} to use for scheduling
* the emission of the complete notification.
* @return {Observable} An "empty" Observable: emits only the complete
* notification.
* @static true
* @name empty
* @owner Observable
*/
static create(scheduler) {
return new EmptyObservable(scheduler);
}
static dispatch(arg) {
const { subscriber } = arg;
subscriber.complete();
}
/** @deprecated internal use only */ _subscribe(subscriber) {
const scheduler = this.scheduler;
if (scheduler) {
return scheduler.schedule(EmptyObservable.dispatch, 0, { subscriber });
}
else {
subscriber.complete();
}
}
}
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