OOP method to access variables of the derived class !!!

We typically use virtual set_() and get_() methods to access the variables added in the extended class from the base class. class handles are created using the base class and type and instance factory overrides are used to replace the class handles respectively. Any reference to the derived class variable from base class is done using virtual set_() and get_() methods which are just empty methods in the base class. At runtime the derived class virtual methods are linked and variables are written or read using set and get methods after a type or instance override.