| import { Observable } from '../Observable'; |
| import { Operator } from '../Operator'; |
| import { Subscriber } from '../Subscriber'; |
| import { EmptyError } from '../util/EmptyError'; |
| import { OperatorFunction } from '../../internal/types'; |
| import { filter } from './filter'; |
| import { takeLast } from './takeLast'; |
| import { throwIfEmpty } from './throwIfEmpty'; |
| import { defaultIfEmpty } from './defaultIfEmpty'; |
| import { identity } from '../util/identity'; |
| |
| /* tslint:disable:max-line-length */ |
| export function last<T, D = T>( |
| predicate?: null, |
| defaultValue?: D |
| ): OperatorFunction<T, T | D>; |
| export function last<T, S extends T>( |
| predicate: (value: T, index: number, source: Observable<T>) => value is S, |
| defaultValue?: S |
| ): OperatorFunction<T, S>; |
| export function last<T, D = T>( |
| predicate: (value: T, index: number, source: Observable<T>) => boolean, |
| defaultValue?: D |
| ): OperatorFunction<T, T | D>; |
| /* tslint:enable:max-line-length */ |
| |
| /** |
| * Returns an Observable that emits only the last item emitted by the source Observable. |
| * It optionally takes a predicate function as a parameter, in which case, rather than emitting |
| * the last item from the source Observable, the resulting Observable will emit the last item |
| * from the source Observable that satisfies the predicate. |
| * |
| * ![](last.png) |
| * |
| * @throws {EmptyError} Delivers an EmptyError to the Observer's `error` |
| * callback if the Observable completes before any `next` notification was sent. |
| * @param {function} [predicate] - The condition any source emitted item has to satisfy. |
| * @param {any} [defaultValue] - An optional default value to provide if last |
| * predicate isn't met or no values were emitted. |
| * @return {Observable} An Observable that emits only the last item satisfying the given condition |
| * from the source, or an NoSuchElementException if no such items are emitted. |
| * @throws - Throws if no items that match the predicate are emitted by the source Observable. |
| */ |
| export function last<T, D>( |
| predicate?: ((value: T, index: number, source: Observable<T>) => boolean) | null, |
| defaultValue?: D |
| ): OperatorFunction<T, T | D> { |
| const hasDefaultValue = arguments.length >= 2; |
| return (source: Observable<T>) => source.pipe( |
| predicate ? filter((v, i) => predicate(v, i, source)) : identity, |
| takeLast(1), |
| hasDefaultValue ? defaultIfEmpty<T | D>(defaultValue) : throwIfEmpty(() => new EmptyError()), |
| ); |
| } |