原始版本：
template<typename T>
void swap(T& a, T& b)
{
T tmp(a);
a = b;
b = tmp;
}
此版本不重视效率，当交换的两个对象比较大时，需要更高效的交换，因此应该提供1）public swap成员函数，让它高效的置换两个对象，并提供nono-member swap,调用之
///////////////////////////////////////////////////////////////////////////////
//
// FileName : swap_item25.h
// Version : 0.10
// Author : Ryan Han
// Date : 2013/07/26 13:13:55
// 2013/10/30 08:27:50
// Comment :
// ½«WidgetÉùÃ÷Ò»¸öswapµÄpublicº¯Êý×öÕæÕýµÄÖû»¹¤×÷£¬È»ºó½«std::swapÌØ»¯
/////////////////////////////////////////////////////////////////////////////// #ifndef _SWAP_ITEM25_H_
#define _SWAP_ITEM25_H_ #include <iostream>
using namespace std; class WidgetImpl {
public:
WidgetImpl(int a = , int b = , int c = );
/*WidgetImpl(int a = 1, int b = 2, int c = 3) : x(a), y(b), z(c){
cout << "WidgetImpl constructor called." << endl;
}*/ ~WidgetImpl(){
cout << "WidgetImpl de-constructor called." << endl;
} void WidgetPrint(){
cout << "x = " << x << " y = " << y << " z = "<< z << endl;
}
private:
int x, y, z;
}; class Widget {
public:
Widget(int a = , int b = , int c = ) : pImpl(new WidgetImpl(a, b, c)){
cout << "Widget constructor called." << endl;
;
} ~Widget(){
cout << "Widget de-constructor called." << endl;
delete pImpl;
} Widget(const Widget& rhs) {
pImpl = new WidgetImpl(*(rhs.pImpl));
} Widget& operator=(const Widget& rhs){
*pImpl = *(rhs.pImpl);
} void WidgetPrint(){
pImpl->WidgetPrint();
//non friend class can't access private data
//cout << (*pImpl).x << endl;
} //has to use because only member function could access private member pImpl
void swap(Widget& other){
using std::swap;
swap(pImpl, other.pImpl);
}
private:
WidgetImpl* pImpl;
}; //inline to avoid duplicate definition
//http://www.cnblogs.com/dracohan/p/3401660.html
namespace std {
template <>
inline void swap<Widget>(Widget& a, Widget& b){
cout << "specialized swap was called" << endl;
a.swap(b);
}
} #endif
///////////////////////////////////////////////////////////////////////////////
//
// FileName : swap_item25.cpp
// Version : 0.10
// Author : Ryan Han
// Date : 2013/07/26 13:13:55
// 2013/10/30 08:27:50
// Comment :
//
/////////////////////////////////////////////////////////////////////////////// #include "swap_item25.h"
#include <iostream>
using namespace std; WidgetImpl::
WidgetImpl(int a, int b, int c) : x(a), y(b), z(c){
cout << "WidgetImpl constructor called." << endl;
}
///////////////////////////////////////////////////////////////////////////////
//
// FileName : swap_item25.cpp
// Version : 0.10
// Author : Ryan Han
// Date : 2013/07/26 13:13:55
// 2013/10/30 08:27:50
// Comment :
//
/////////////////////////////////////////////////////////////////////////////// #include "swap_item25.h"
#include <iostream>
using namespace std; int main()
{
Widget a;
Widget b(,,); a.WidgetPrint();
b.WidgetPrint(); swap(a, b); a.WidgetPrint();
b.WidgetPrint(); int* pinta = new int();
int* pintb = pinta; cout << "*pinta is: " << *pinta << endl;
cout << "*pintb is: " << *pintb << endl; return ;
}