53 lines
2.1 KiB
TypeScript
53 lines
2.1 KiB
TypeScript
|
import { Observable } from '../Observable';
|
||
|
|
import { ObservedValueOf, ObservableInput } from '../types';
|
||
|
|
/**
|
||
|
|
* Creates an Observable that, on subscribe, calls an Observable factory to
|
||
|
|
* make an Observable for each new Observer.
|
||
|
|
*
|
||
|
|
* <span class="informal">Creates the Observable lazily, that is, only when it
|
||
|
|
* is subscribed.
|
||
|
|
* </span>
|
||
|
|
*
|
||
|
|
* 
|
||
|
|
*
|
||
|
|
* `defer` allows you to create the Observable only when the Observer
|
||
|
|
* subscribes, and create a fresh Observable for each Observer. It waits until
|
||
|
|
* an Observer subscribes to it, and then it generates an Observable,
|
||
|
|
* typically with an Observable factory function. It does this afresh for each
|
||
|
|
* subscriber, so although each subscriber may think it is subscribing to the
|
||
|
|
* same Observable, in fact each subscriber gets its own individual
|
||
|
|
* Observable.
|
||
|
|
*
|
||
|
|
* ## Example
|
||
|
|
* ### Subscribe to either an Observable of clicks or an Observable of interval, at random
|
||
|
|
* ```ts
|
||
|
|
* import { defer, fromEvent, interval } from 'rxjs';
|
||
|
|
*
|
||
|
|
* const clicksOrInterval = defer(function () {
|
||
|
|
* return Math.random() > 0.5
|
||
|
|
* ? fromEvent(document, 'click')
|
||
|
|
* : interval(1000);
|
||
|
|
* });
|
||
|
|
* clicksOrInterval.subscribe(x => console.log(x));
|
||
|
|
*
|
||
|
|
* // Results in the following behavior:
|
||
|
|
* // If the result of Math.random() is greater than 0.5 it will listen
|
||
|
|
* // for clicks anywhere on the "document"; when document is clicked it
|
||
|
|
* // will log a MouseEvent object to the console. If the result is less
|
||
|
|
* // than 0.5 it will emit ascending numbers, one every second(1000ms).
|
||
|
|
* ```
|
||
|
|
*
|
||
|
|
* @see {@link Observable}
|
||
|
|
*
|
||
|
|
* @param {function(): SubscribableOrPromise} observableFactory The Observable
|
||
|
|
* factory function to invoke for each Observer that subscribes to the output
|
||
|
|
* Observable. May also return a Promise, which will be converted on the fly
|
||
|
|
* to an Observable.
|
||
|
|
* @return {Observable} An Observable whose Observers' subscriptions trigger
|
||
|
|
* an invocation of the given Observable factory function.
|
||
|
|
* @static true
|
||
|
|
* @name defer
|
||
|
|
* @owner Observable
|
||
|
|
*/
|
||
|
|
export declare function defer<R extends ObservableInput<any> | void>(observableFactory: () => R): Observable<ObservedValueOf<R>>;
|