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This article discusses the implementation of class templates in C++ using Runtime Type Information (RTTI). It demonstrates how templates work effectively with RTTI to generate classes. The example illustrates a template class `Announce` that prints the class name during construction and destruction. The derived class `X` shows the use of inheritance and composition, producing an interesting order of constructor and destructor calls. The output showcases RTTI support in action, helping better understand class management in C++.
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RTTI AND TEMPLATES • Class templates work well with RTTI, since all they do is generate classes. • As usual, RTTI provides a convenient way to obtain the name of the class .
#include <iostream> #include <typeinfo> using namespace std; template<int id> class Announce { public: Announce() { cout << typeid(*this).name() << " constructor" << endl; }
~Announce() { cout << typeid(*this).name() << " destructor" << endl; } }; class X : public Announce<0> { Announce<1> m1; Announce<2> m2;
public: X() { cout << "X::X()" << endl; } ~X() { cout << "X::~X()" << endl; } }; int main() { X x; }
This template uses a constant int to differentiate one class from another, but type arguments would work as well. • Inside both the constructor and destructor, RTTI information produces the name of the class to print. • The class X uses both inheritance and composition to create a class that has an interesting order of constructor and destructor calls.
The output is Announce<0> constructor Announce<1> constructor Announce<2> constructor X::X() X::~X() Announce<2> destructor Announce<1> destructor Announce<0> destructor Of course, you may get different output depending on how your compiler represents its name( ) information
