Category 

C++-Specific Keywords 

Description 

In the expression, dynamic_cast< T > (ptr), T must be a pointer or a reference to a defined class type or void*. The argument ptr must be an expression that resolves to a pointer or reference. 

If T is void* then ptr must also be a pointer. In this case, the resulting pointer can access any element of the class that is the most derived element in the hierarchy. Such a class cannot be a base for any other class. 

Conversions from a derived class to a base class, or from one derived class to another, are as follows: if T is a pointer and ptr is a pointer to a non-base class that is an element of a class hierarchy, the result is a pointer to the unique subclass. References are treated similarly. If T is a reference and ptr is a reference to a non-base class, the result is a reference to the unique subclass. 

A conversion from a base class to a derived class can be performed only if the base is a polymorphic type. 

The conversion to a base class is resolved at compile time. A conversion from a base class to a derived class, or a conversion across a hierarchy is resolved at runtime. 

If successful, dynamic_cast< T > (ptr) converts ptr to the desired type. If a pointer cast fails, the returned pointer is valued 0. If a cast to a reference type fails, the Bad_cast exception is thrown.