import { Observable } from '../Observable';
/**
 * 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>
 *
 * <img src="./img/pluck.png" width="100%">
 *
 * 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 <caption>Map every click to the tagName of the clicked target element</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var tagNames = clicks.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 declare function pluck<T, R>(this: Observable<T>, ...properties: string[]): Observable<R>;