C++ (Qt)
struct CObjectParam {
  COpenGLObject * mObject;
  QVariantList mParams;          
};
 
void CWindow::registerParamProcessor( int type, std::function< bool( CObjectParam* o, const QVariant& v ) > f )
{
   mParamProcessors[ type ] = f;
}
 
void CWindow::Draw( ... )
{
 for (int i = 0; i < mObjects.size(); ++i) {
   auto& obj = mObjects[i];
   for( auto& v : obj->mParams ) {
      auto f = mParamProcessors[ v.userType() ];
      if( !f( obj, v ) )
          break;
   }
 }
}