swap函数的例子

#include<iostream>
#include<string>
#include<new>
#include<vector>
#include<algorithm>

using namespace std;
class HasPtr
{
friend void swap(HasPtr&,HasPtr&);
public:
    HasPtr(const string &s=string()):ps(new string(s)),i(0){cout<<"constructer"<<endl;}
    HasPtr(const HasPtr &h):i(h.i)
    {
        cout<<"copy constructer"<<endl;
        ps=new string;
        *ps=*h.ps;//只拷贝值
    }
    HasPtr& operator=(HasPtr h)
    {
        swap(*this,h);
        return *this;
    }
    bool operator<(const HasPtr &h) const
    {
        return i<h.i;
    }
    ~HasPtr() {  delete ps; cout<<"destructer"<<endl;}
private:
    string *ps;
    int i;
};
void swap(HasPtr &lhs,HasPtr &rhs)
{
    cout<<"swap"<<endl;
    using std::swap;
    swap(lhs.ps,rhs.ps);
    swap(lhs.i,rhs.i);
}
int main()
{
    HasPtr h;
    HasPtr hh(h);
    hh=h;
    swap(h,hh);
    vector<HasPtr> vec={h,hh};
    sort(vec.begin(),vec.end());
    return 0;
}