代理模式 Proxy

#include <IOSTREAM>
using namespace std;

template<class T>
class auto_ptr{
public:
explicit auto_ptr(T * p = 0){
preal = p;
}
auto_ptr(auto_ptr<T> & pother)
:preal(pother.release()){

}
T * release(){                      //释放智能指针对其指针的拥有权，使preal = 0
T * pold = preal;
preal = 0;
return pold;
}

void reset(T * p = 0){
if(preal != p){
delete preal;
preal = p;
}
}

~auto_ptr(){
delete preal;
}

T * get(){
return preal;
}

auto_ptr<T> & operator=(auto_ptr<T> & pother ){
if( &pother != this){ //pother != *this,没有重载!=符号,会出错
reset(pother.release());
}
return *this;
}
private:
T * preal;
};
int main(int argc, char* argv[])
{
auto_ptr<int> a(new int(5));
cout<<*a.get()<<endl;
auto_ptr<int> b(a);
//    cout<<*a.get()<<endl;  出错，已经转移所有权至b
cout<<*b.get()<<endl;
a = a;
b = b;
//    cout<<*a.get()<<endl;
return 0;
}