C++ 11 feature: dynamic_cast with RTTI

“dynamic_cast” is new concept in C++ 11.

dynamic_cast is used at runtime to check the correctness of down casting.

As it checks the correctness at runtime, it is slower than “static_cast”.

“dynamic_cast” is used in handling polymorphism.

“dynamic_cast” will return the object if the cast is correct else it will return NULL.

Note:

There should be atleast 1 virtual function for “dynamic_cast” to work.

Consider below scenario where “dynamic_cast” is useful:

There is a Base class and 2 derived classes D1 and D2.

Now we have upcasted the derived class D1 object to base class pointer and then downcasted that base pointer to derived class 2 object. This is an error, you cannot do it. As both of the object belongs to 2 different objects.

Syntax of dynamic_cast cast:

data_type *var_name = dynamic_cast <data_type *>(pointer_variable);

Example:

#include <iostream>
#include <set>
//for more C++ tutorial visit www.ProDeveloperTutorial.com
using namespace std;

class Base
{
    public:
    virtual void print()
    {
        
    }
};

class Derived_1: public Base
{
    
};

class Derived_2: public Base
{
    
};

int main(void) 
{ 
    Derived_1 d1;
    
    Base *bp = dynamic_cast<Base*> (&d1);
    
    Derived_2 *d2 = dynamic_cast<Derived_2*> (bp);
    
    if(d2 == nullptr)
    {
        cout<<"Casting did not occur"<<endl;
    }
    else
    {
        cout<<"Casting occur"<<endl;
    }
    
    return 0; 
} 

Output:

Casting did not occur

Note:

dynamic_cast is used with pointer and reference to object only.

RTTI: Runtime Tyoe Information:

C++ has given a standard wat to determine the type of object at runtime.

RTTI can be found by using 2 operations:

1. typeid(variable).name()

2. dynamic_cast