import { z } from 'zod';
import { EntityC } from './types';
/**
 * A reference to another entity.
 *
 * ### Examples
 *
 * ```
 * Ref.to(User).through(user => user.id);
 * ```
 */
export declare class Ref<C extends EntityC> {
    private readonly Entity;
    static to<C extends EntityC>(Entity: C): Ref<C>;
    private constructor();
    through<U>(mapping: (entity: z.TypeOf<C>) => U): U;
}