| import { Observable } from '../Observable'; |
| import { map } from './map'; |
| import { OperatorFunction } from '../types'; |
| |
| /* tslint:disable:max-line-length */ |
| export function pluck<T, K1 extends keyof T>(k1: K1): OperatorFunction<T, T[K1]>; |
| export function pluck<T, K1 extends keyof T, K2 extends keyof T[K1]>(k1: K1, k2: K2): OperatorFunction<T, T[K1][K2]>; |
| export function pluck<T, K1 extends keyof T, K2 extends keyof T[K1], K3 extends keyof T[K1][K2]>(k1: K1, k2: K2, k3: K3): OperatorFunction<T, T[K1][K2][K3]>; |
| export function pluck<T, K1 extends keyof T, K2 extends keyof T[K1], K3 extends keyof T[K1][K2], K4 extends keyof T[K1][K2][K3]>(k1: K1, k2: K2, k3: K3, k4: K4): OperatorFunction<T, T[K1][K2][K3][K4]>; |
| export function pluck<T, K1 extends keyof T, K2 extends keyof T[K1], K3 extends keyof T[K1][K2], K4 extends keyof T[K1][K2][K3], K5 extends keyof T[K1][K2][K3][K4]>(k1: K1, k2: K2, k3: K3, k4: K4, k5: K5): OperatorFunction<T, T[K1][K2][K3][K4][K5]>; |
| export function pluck<T, K1 extends keyof T, K2 extends keyof T[K1], K3 extends keyof T[K1][K2], K4 extends keyof T[K1][K2][K3], K5 extends keyof T[K1][K2][K3][K4], K6 extends keyof T[K1][K2][K3][K4][K5]>(k1: K1, k2: K2, k3: K3, k4: K4, k5: K5, k6: K6): OperatorFunction<T, T[K1][K2][K3][K4][K5][K6]>; |
| export function pluck<T, R>(...properties: string[]): OperatorFunction<T, R>; |
| /* tslint:enable:max-line-length */ |
| |
| /** |
| * Maps each source value (an object) to its specified nested property. |
| * |
| * <span class="informal">Like {@link map}, but meant only for picking one of |
| * the nested properties of every emitted object.</span> |
| * |
| * ![](pluck.png) |
| * |
| * Given a list of strings describing a path to an object property, retrieves |
| * the value of a specified nested property from all values in the source |
| * Observable. If a property can't be resolved, it will return `undefined` for |
| * that value. |
| * |
| * ## Example |
| * Map every click to the tagName of the clicked target element |
| * ```ts |
| * import { fromEvent } from 'rxjs'; |
| * import { pluck } from 'rxjs/operators'; |
| * |
| * const clicks = fromEvent(document, 'click'); |
| * const tagNames = clicks.pipe(pluck('target', 'tagName')); |
| * tagNames.subscribe(x => console.log(x)); |
| * ``` |
| * |
| * @see {@link map} |
| * |
| * @param {...string} properties The nested properties to pluck from each source |
| * value (an object). |
| * @return {Observable} A new Observable of property values from the source values. |
| * @method pluck |
| * @owner Observable |
| */ |
| export function pluck<T, R>(...properties: string[]): OperatorFunction<T, R> { |
| const length = properties.length; |
| if (length === 0) { |
| throw new Error('list of properties cannot be empty.'); |
| } |
| return (source: Observable<T>) => map(plucker(properties, length))(source as any); |
| } |
| |
| function plucker(props: string[], length: number): (x: string) => any { |
| const mapper = (x: string) => { |
| let currentProp = x; |
| for (let i = 0; i < length; i++) { |
| const p = currentProp[props[i]]; |
| if (typeof p !== 'undefined') { |
| currentProp = p; |
| } else { |
| return undefined; |
| } |
| } |
| return currentProp; |
| }; |
| |
| return mapper; |
| } |