bad_cast class

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Header File

typeinfo.h

Description

When dynamic_cast fails to make a cast to reference, the expression can throw bad_cast class. Note that when dynamic_cast fails to make a cast to pointer type, the result is the null pointer.

Example

How to perform run-time type identification

#include <iostream>
#include <typeinfo.h>
 
using std::cout;
 
class __rtti Alpha {
   virtual void func() {};  // This makes Alpha a polymorphic class type.
};
 
class B : public Alpha {};
 
int main(void)
{
   B Binst;           // Instantiate class B
   B *Bptr;           // Declare a B-type pointer
   Bptr = &Binst;     // Initialize the pointer
 
   // THESE TESTS ARE DONE AT RUN TIME
 
   // Ask "WHAT IS THE TYPE FOR *Bptr?"
 
   if (typeid( *Bptr ) == typeid( B ) )
       cout << "Name is " << typeid( *Bptr).name();
 
   if (typeid( *Bptr ) != typeid( Alpha ) )
       cout << "\nPointer is not an Alpha-type.";
 
   return 0;
}

Program output:

Name is B
Pointer is not an Alpha-type.