C++ Primer Plus

Misusing RTTI

RTTI has many vocal critics within the C++ community. They view RTTI as unnecessary, a potential source of program inefficiency, and a possible contributor to bad programming practices. Without delving into the debate over RTTI, let’s look at the sort of programming that you should avoid.

Consider the core of Listing 15.17:

Grand * pg;Superb * ps;for (int i = 0; i < 5; i++){    pg = GetOne();    pg->Speak();    if( ps = dynamic_cast<Superb *>(pg))         ps->Say();}

By using typeid and ignoring dynamic_cast and virtual functions, you can rewrite this code as follows:

Grand * pg;Superb * ps;Magnificent * pm;for (int i = 0; i < 5; i++){    pg = GetOne();    if (typeid(Magnificent) == typeid(*pg))    {        pm = (Magnificent *) ...