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keksAccountGUI/node_modulesOLD/rxjs/internal/operators/single.d.ts
2019-08-11 20:48:02 +02:00

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1.9 KiB
TypeScript

import { Observable } from '../Observable';
import { MonoTypeOperatorFunction } from '../types';
/**
* Returns an Observable that emits the single item emitted by the source Observable that matches a specified
* predicate, if that Observable emits one such item. If the source Observable emits more than one such item or no
* items, notify of an IllegalArgumentException or NoSuchElementException respectively. If the source Observable
* emits items but none match the specified predicate then `undefined` is emitted.
*
* <span class="informal">Like {@link first}, but emit with error notification if there is more than one value.</span>
* ![](single.png)
*
* ## Example
* emits 'error'
* ```ts
* import { range } from 'rxjs';
* import { single } from 'rxjs/operators';
*
* const numbers = range(1,5).pipe(single());
* numbers.subscribe(x => console.log('never get called'), e => console.log('error'));
* // result
* // 'error'
* ```
*
* emits 'undefined'
* ```ts
* import { range } from 'rxjs';
* import { single } from 'rxjs/operators';
*
* const numbers = range(1,5).pipe(single(x => x === 10));
* numbers.subscribe(x => console.log(x));
* // result
* // 'undefined'
* ```
*
* @see {@link first}
* @see {@link find}
* @see {@link findIndex}
* @see {@link elementAt}
*
* @throws {EmptyError} Delivers an EmptyError to the Observer's `error`
* callback if the Observable completes before any `next` notification was sent.
* @param {Function} predicate - A predicate function to evaluate items emitted by the source Observable.
* @return {Observable<T>} An Observable that emits the single item emitted by the source Observable that matches
* the predicate or `undefined` when no items match.
*
* @method single
* @owner Observable
*/
export declare function single<T>(predicate?: (value: T, index: number, source: Observable<T>) => boolean): MonoTypeOperatorFunction<T>;