51virtualfunc.cpp

#include <iostream>
using namespace std;

class BaseClass
{
public:
    int var_base = 9;
    virtual void display() // the virtual here told the compiler to seek the other display of the object's class and not of the pointer
    {
        cout << "Base class variable var_base value is " << var_base << endl;
    }
};

class DerivedClass : public BaseClass
{
public:
    int var_derived = 10;
    void display()
    {
        cout << "Base class variable var_base value is " << var_base << endl;
        cout << "Derived class variable var_derived value is " << var_derived << endl;
    }
};
int main()
{

    BaseClass *base_class_pointer;
    BaseClass obj_base;
    DerivedClass obj_derived;
    base_class_pointer = &obj_derived;

    /*
    for the base class pointer pointing to derived class object to access the derived class function of the same name,
    use virtual before the base class function
    this creates a virtual function
        it tells the compiler that there is another function with the same name in the object's class so use that instead
    */
    base_class_pointer->display();
    return 0;
}