import { IFile } from './interfaces';
/**
 * Interface describing FileValidators, which can be added to a ParseFilePipe
 *
 * @see {ParseFilePipe}
 * @publicApi
 */
export declare abstract class FileValidator<TValidationOptions = Record<string, any>, TFile extends IFile = IFile> {
    protected readonly validationOptions: TValidationOptions;
    constructor(validationOptions: TValidationOptions);
    /**
     * Indicates if this file should be considered valid, according to the options passed in the constructor.
     * @param file the file from the request object
     */
    abstract isValid(file?: TFile | TFile[] | Record<string, TFile[]>): boolean | Promise<boolean>;
    /**
     * Builds an error message in case the validation fails.
     * @param file the file from the request object
     */
    abstract buildErrorMessage(file: any): string;
}