Pointers to Derived Classes and Base Classes

Pointers to Derived Classes and Base Classes

1) Pointer to Derived Class

We can declared a pointer

#include <iostream>

using namespace std;

class Base {

public:

void showBase(){

        cout<<"\n Base class Function!";

}

};

class Derived:public Base {

public:

void showDerived(){

        cout<<"\n Derived class Function!";

}

};

int main()

{

Derived obj;

Derived *ptr = &obj;

 ptr‒>showBase();

return 0;

}

Output

Base class Function!

Derived class Function!

Code Explantion : Note that in above program, the type of pointer variable ptr is Derived *. Hence it is a pointer to derived class.

2) Pointer to Base Class

•  A pointer of type base class can point to both the base class object as well as a  derived class object. But by default it can only access base class members. For

example ‒

#include <iostream>

using namespace std;

class Base {

public:

void showBase(){

       cout<<"\n Base class Function!";

}

};

class Derived:public Base {

public:

void showDerived(){

      cout<<"\n Derived class Function!";

}

};

int main(){

Derived obj;

Base *ptr = &obj;

ptr‒>showBase();

ptr‒>showDerived();   //Error as base pointer does not know about derived class function

return 0;

}

Code Explanation: In above code we have defined a base class pointer using a variable ptr. Since pointer is of type base class it can not access the function defined in the derived class. Hence we get error on execution of above program