use-handle.cpp

C++Primer 经典之作

/*
 * This file contains code from "C++ Primer, Fourth Edition", by Stanley B.
 * Lippman, Jose Lajoie, and Barbara E. Moo, and is covered under the
 * copyright and warranty notices given in that book:
 * 
 * "Copyright (c) 2005 by Objectwrite, Inc., Jose Lajoie, and Barbara E. Moo."
 * 
 * 
 * "The authors and publisher have taken care in the preparation of this book,
 * but make no expressed or implied warranty of any kind and assume no
 * responsibility for errors or omissions. No liability is assumed for
 * incidental or consequential damages in connection with or arising out of the
 * use of the information or programs contained herein."
 * 
 * Permission is granted for this code to be used for educational purposes in
 * association with the book, given proper citation if and when posted or
 * reproduced.Any commercial use of this code requires the explicit written
 * permission of the publisher, Addison-Wesley Professional, a division of
 * Pearson Education, Inc. Send your request for permission, stating clearly
 * what code you would like to use, and in what specific way, to the following
 * address: 
 * 
 * 	Pearson Education, Inc.
 * 	Rights and Contracts Department
 * 	75 Arlington Street, Suite 300
 * 	Boston, MA 02216
 * 	Fax: [phone]
*/ 

#include <iostream>
using std::cout; using std::endl;

#include "Handle.h"

int main()
{
{  // new scope
   // user allocates but must not delete the object to which the Handle is attached
   Handle<int> hp(new int(42));
   { // new scope
       Handle<int> hp2 = hp;   // copies pointer; use count incremented
       cout << *hp << " " << *hp2 << endl;   // prints 42 42
       *hp2 = 10;              // changes value of shared underlying int
   }   // hp2 goes out of scope; use count is decremented
   cout << *hp << endl;    // prints 10
}  // hp goes out of scope; its destructor deletes the int
}