Attempt to read property “ConnID” on bool

i was checking the affected_rows but i experience such bug from my model. my model code below

namespace AppModels;

use CodeIgniterModel;

class ContactModel extends Model {
    public function saveData($data)
    {
        $db= ConfigDatabase::connect();
        $builder = $db->table('message');
        $res = $builder->insert($data);
        if ($res->connID->affected_rows>=1) 
        {
            return true;
        } 
        else 
        {
            return false;
        }
    }
}