/**
* 根据user_id查找头像
* @param integer $user_id
* @return UserAvatar the loaded model
* @throws NotFoundHttpException if the model cannot be found
*/
protected function findModel($user_id)
{
if (($model = UserAvatar::findOne(['user_id' => $user_id])) !== null) {
return $model;
} else {
return null;
}
}
