public function validate($attribute, $value, $parameters, $validator)
    {
        list ($name, $locale) = $this->getAttributeNameAndLocale($attribute);

        if ($this->isUnique($value, $name, $locale, $parameters)) {
            return true;
        }

        $this->addErrorsToValidator($validator, $parameters, $name, $locale);

        return false;
    }