import { Rule, RuleConfig } from '../validationRules';
export interface RequireRuleConfig extends RuleConfig {
    /**
     * For some fields a blank is not an empty value. Allow for setting
     * alternative values that are also considered as being empty.
     */
    alternativeEmpties?: Array<string>;
}
export declare class RequireRule extends Rule {
    config: RequireRuleConfig;
    defaultMessage: string;
    constructor(config: RequireRuleConfig);
    /**
     * Required rule makes the field required.
     */
    get isRequired(): boolean;
    validate(value: any): string | null;
}