Mega Code Archive
Template counter
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/* The following code example is taken from the book
* "C++ Templates - The Complete Guide"
* by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
*
* (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <stddef.h>
template <typename CountedType>
class ObjectCounter {
private:
static size_t count; // number of existing objects
protected:
// default constructor
ObjectCounter() {
++count;
}
// copy constructor
ObjectCounter (ObjectCounter<CountedType> const&) {
++count;
}
// destructor
~ObjectCounter() {
--count;
}
public:
// return number of existing objects:
static size_t live() {
return count;
}
};
// initialize counter with zero
template <typename CountedType>
size_t ObjectCounter<CountedType>::count = 0;
template <typename CharT>
class MyString : public ObjectCounter<MyString<CharT> > {
//...
};
int main()
{
MyString<char> s1, s2;
MyString<wchar_t> ws;
std::cout << "number of MyString<char>: "
<< MyString<char>::live() << std::endl;
std::cout << "number of MyString<wchar_t>: "
<< ws.live() << std::endl;
}
number of MyString: 2
number of MyString: 1
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