Upcasting: It is the process of converting derived-class reference or pointer to the base class.
Downcasting: It is the process of converting base-class reference or pointer to the derived class.
Upcasting:
Here the derived class pointer is converted to base class.
This is allowed in inheritance.
There is no need of explicit typecasting.
There is an is-a relationship between the base class and derived class.
Object-slicing can occur in upcasting.
Example of upcasting:
#include <iostream> // std::cout
// for more tutorials visit www.ProDeveloperTutorial.com
using namespace std;
class Base
{
public:
void baseFun()
{
cout<<"Base Function"<<endl;
}
};
class Derived: public Base
{
public:
void derivedFun()
{
cout<<"Derived Fun"<<endl;
}
};
int main( )
{
Derived dObj;
//upcasting - implicit upcasting is allowed
Base *bPtr = &dObj;
bPtr -> baseFun();
return 0;
}Output:
Base Function
Downcasting:
It converts base class pointer to derived class pointer.
You need to explicitly type cast during downcasting.
#include <iostream> // std::cout
// for more tutorials visit www.ProDeveloperTutorial.com
using namespace std;
class Base
{
public:
void baseFun()
{
cout<<"Base Function"<<endl;
}
};
class Derived: public Base
{
public:
void derivedFun()
{
cout<<"Derived Fun"<<endl;
}
};
int main( )
{
Base bObj;
// explicit type cast is required
Derived *dPtr = (Derived *) &bObj;
dPtr -> derivedFun();
return 0;
}
Output:
Derived Fun
