protected function initFields()
{
$fields = static::fields();
foreach ($fields as $field => $opts) {
if (!isset($this->_data[$field])) {
$this->_data[$field] = isset($opts['value']) ? $opts['value'] : null;
}
}
$entityName = get_class($this);
if (!isset(self::$relationFields[$entityName])) {
self::$relationFields[$entityName] = [];
}
}