C++ In a Nutshell

Name

dynamic_cast operator — Polymorphic cast of class type objects

Synopsis

               postfix-expr := dynamic_cast < type-id > ( expression )

The dynamic_cast operator performs a polymorphic cast on a pointer or reference to an object of class type. If expression is a pointer or reference to a base class, type-id can be a pointer or reference to a derived class. If the dynamic type of the object is not that of type-id or a class derived from type-id, the cast fails. If expression is a pointer, failure returns a null pointer; if expression is a reference, failure throws std::bad_cast. Casts from a derived to an unambiguous, accessible base class always succeed.

If expression is a null pointer, the result is a null pointer. If type-id is a pointer to void, the cast succeeds and returns a pointer to the most-derived object that expression represents.

Example

struct base {};
struct derived : base {};
base* b = new derived;
derived* d =dynamic_cast<derived*>(b);

See Also

const_cast, expression, reinterpret_cast, static_cast, type, Chapter 3, <typeinfo>