/* 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.
*/
template
class Holder {
private:
T* ptr; // refers to the object it holds (if any)
public:
// default constructor: let the holder refer to nothing
Holder() : ptr(0) {
}
// constructor for a pointer: let the holder refer to where the pointer refers
explicit Holder (T* p) : ptr(p) {
}
// destructor: releases the object to which it refers (if any)
~Holder() {
delete ptr;
}
// assignment of new pointer
Holder& operator= (T* p) {
delete ptr;
ptr = p;
return *this;
}
// pointer operators
T& operator* () const {
return *ptr;
}
T* operator-> () const {
return ptr;
}
// get referenced object (if any)
T* get() const {
return ptr;
}
// release ownership of referenced object
void release() {
ptr = 0;
}
// exchange ownership with other holder
void exchange_with (Holder& h) {
swap(ptr,h.ptr);
}
// exchange ownership with other pointer
void exchange_with (T*& p) {
swap(ptr,p);
}
private:
// no copying and copy assignment allowed
Holder (Holder const&);
Holder& operator= (Holder const&);
};
class Something {
public:
void perform() const {
}
};
void do_two_things()
{
Holder first(new Something);
first->perform();
Holder second(new Something);
second->perform();
}
int main()
{
do_two_things();
}