import { StringRuleChecker } from './string-rule-checker';
import { JsonFormat } from './string-types';
import { GuardResult } from '../../core/guard-result';
export declare class StringIsJson extends StringRuleChecker<{
    type: 'isJson';
    format?: JsonFormat;
}> {
    constructor(rule: {
        type: 'isJson';
        format?: JsonFormat;
    }, value: string);
    /**
     * @override
     */
    exec(): GuardResult;
    private isJsonArray;
    private isJsonObject;
    private isJsonString;
    private isJson;
}