public function beforeValidate()
    {
        $this->fileName = $this->owner->getAttribute($this->fileField);
        if (!is_string($this->fileName)) {
            $this->fileName = @$this->owner->oldAttributes[$this->fileField];
        }
        if (
            (!$files = UploadedFile::getInstance($this->owner, $this->fileField))
            && (!$files = UploadedFile::getInstances($this->owner, $this->fileField))     
        ) {
            return true;
        }
        return $this->owner->setAttribute($this->fileField, $files);
    }