| 1 | import { Observable } from '../Observable';
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| 2 | import { ObservedValueOf, ObservableInput } from '../types';
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| 3 | /**
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| 4 | * Creates an Observable that, on subscribe, calls an Observable factory to
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| 5 | * make an Observable for each new Observer.
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| 6 | *
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| 7 | * <span class="informal">Creates the Observable lazily, that is, only when it
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| 8 | * is subscribed.
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| 9 | * </span>
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| 10 | *
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| 11 | * 
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| 12 | *
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| 13 | * `defer` allows you to create the Observable only when the Observer
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| 14 | * subscribes, and create a fresh Observable for each Observer. It waits until
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| 15 | * an Observer subscribes to it, and then it generates an Observable,
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| 16 | * typically with an Observable factory function. It does this afresh for each
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| 17 | * subscriber, so although each subscriber may think it is subscribing to the
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| 18 | * same Observable, in fact each subscriber gets its own individual
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| 19 | * Observable.
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| 20 | *
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| 21 | * ## Example
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| 22 | * ### Subscribe to either an Observable of clicks or an Observable of interval, at random
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| 23 | * ```ts
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| 24 | * import { defer, fromEvent, interval } from 'rxjs';
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| 25 | *
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| 26 | * const clicksOrInterval = defer(function () {
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| 27 | * return Math.random() > 0.5
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| 28 | * ? fromEvent(document, 'click')
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| 29 | * : interval(1000);
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| 30 | * });
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| 31 | * clicksOrInterval.subscribe(x => console.log(x));
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| 32 | *
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| 33 | * // Results in the following behavior:
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| 34 | * // If the result of Math.random() is greater than 0.5 it will listen
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| 35 | * // for clicks anywhere on the "document"; when document is clicked it
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| 36 | * // will log a MouseEvent object to the console. If the result is less
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| 37 | * // than 0.5 it will emit ascending numbers, one every second(1000ms).
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| 38 | * ```
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| 39 | *
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| 40 | * @see {@link Observable}
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| 41 | *
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| 42 | * @param {function(): SubscribableOrPromise} observableFactory The Observable
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| 43 | * factory function to invoke for each Observer that subscribes to the output
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| 44 | * Observable. May also return a Promise, which will be converted on the fly
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| 45 | * to an Observable.
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| 46 | * @return {Observable} An Observable whose Observers' subscriptions trigger
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| 47 | * an invocation of the given Observable factory function.
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| 48 | * @static true
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| 49 | * @name defer
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| 50 | * @owner Observable
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| 51 | */
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| 52 | export declare function defer<R extends ObservableInput<any> | void>(observableFactory: () => R): Observable<ObservedValueOf<R>>;
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