What is program written in c plus plus for RTTI?

Answer 1

RTTI (run-time type information) is often necessary when dealing with a hierarchy of classes for which the virtual interface does not provide enough information about the total object from the base class alone.

The chief method of enabling RTTI is to use the dynamic_cast operator. This operator can cast pointers or references to base classes to pointers or references to derived classes. When casting to a pointer, a nullptr indicates the cast failed. When casting to a reference, a bad_cast exception is thrown (because references cannot be null). Thus before dynamically casting a reference, it pays to get some more information about the total object. This is achieved with the typeid operator.

void foo (shape& s)

{

if (typeid (s) == typeid (circle))

{

circle c = dynamic_cast<circle&> (s);

// operate upon c...

}

}

Note that RTTI is often misused. If it is impossible or undesirable to modify the base class to provide a suitable interface, then RTTI may be warranted. However, keep in mind that the problem is not that you are attempting to gain access to an interface that isn't available in the base class, it is that you are attempting to access that interface through the wrong class in the first place. Sometimes that is unavoidable, especially in user-interfaces where the application and system interact through widgets and controls where information can often become lost in the exchange. However, always try and look at alternatives whenever possible before resorting to RTTI as this can often indicate a poor design choice.