Repositorio del curso CCOM4030 el semestre B91 del proyecto Artesanías con el Instituto de Cultura

single.d.ts 1.9KB

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  1. import { Observable } from '../Observable';
  2. import { MonoTypeOperatorFunction } from '../types';
  3. /**
  4. * Returns an Observable that emits the single item emitted by the source Observable that matches a specified
  5. * predicate, if that Observable emits one such item. If the source Observable emits more than one such item or no
  6. * items, notify of an IllegalArgumentException or NoSuchElementException respectively. If the source Observable
  7. * emits items but none match the specified predicate then `undefined` is emitted.
  8. *
  9. * <span class="informal">Like {@link first}, but emit with error notification if there is more than one value.</span>
  10. * ![](single.png)
  11. *
  12. * ## Example
  13. * emits 'error'
  14. * ```ts
  15. * import { range } from 'rxjs';
  16. * import { single } from 'rxjs/operators';
  17. *
  18. * const numbers = range(1,5).pipe(single());
  19. * numbers.subscribe(x => console.log('never get called'), e => console.log('error'));
  20. * // result
  21. * // 'error'
  22. * ```
  23. *
  24. * emits 'undefined'
  25. * ```ts
  26. * import { range } from 'rxjs';
  27. * import { single } from 'rxjs/operators';
  28. *
  29. * const numbers = range(1,5).pipe(single(x => x === 10));
  30. * numbers.subscribe(x => console.log(x));
  31. * // result
  32. * // 'undefined'
  33. * ```
  34. *
  35. * @see {@link first}
  36. * @see {@link find}
  37. * @see {@link findIndex}
  38. * @see {@link elementAt}
  39. *
  40. * @throws {EmptyError} Delivers an EmptyError to the Observer's `error`
  41. * callback if the Observable completes before any `next` notification was sent.
  42. * @param {Function} predicate - A predicate function to evaluate items emitted by the source Observable.
  43. * @return {Observable<T>} An Observable that emits the single item emitted by the source Observable that matches
  44. * the predicate or `undefined` when no items match.
  45. *
  46. * @method single
  47. * @owner Observable
  48. */
  49. export declare function single<T>(predicate?: (value: T, index: number, source: Observable<T>) => boolean): MonoTypeOperatorFunction<T>;