详解C++-(=)赋值操作符、智能指针编写

class Test{
    int *p;
    Test(int i)
    {
       p=new int(i);
    }
    Test& operator = (const Test& obj)
    {
       if(this!=obj)
       {
           delete p;
           p=new int(*obj.p);
       }
       return *this;
    }
};

#include <iostream>
using namespace std;
class Point{
    int *p;
public:
    Point(int *p=NULL)
    {
     this->p = p;
    }
    int* operator -> ()
    {
       return p;
    }
    int& operator *()
    {
       return *p;
    }
    ~Point()
    {
     cout<<"~Point()"<<endl;
     delete p;
    }
};
int main()
{    
    for(int i=0;i<5;i++) 
    {
    Point p=new int(i);
    cout <<*p<<endl;
    }
    return 0;
}

#include <iostream>
using namespace std;
class Point{
    int *p;
public:
    Point(int *p=NULL)
    {
     this->p = p;
    } 
    bool isNULL()
    {
       return (p==NULL);
    }
    int* operator -> ()
    {
       return p;
    }
    int& operator *()
    {
       return *p;
    }
   Point& operator = (const Point& t)
    {
       cout<<"operator =()"<<endl;
       if(this!=&t)
       {
           delete p;
           p = t.p;
           const_cast<Point&>(t).p=NULL;
       }     
       return *this;
    }
    ~Point()
    {
     cout<<"~Point()"<<endl;
     delete p;
    }
};
int main()
{    
    Point p=new int(2);
    Point p2;
    p2= p;     //等价于 p2.operator= (p); 
    cout <<"p=NULL:"<<p.isNULL()<<endl;
    *p2+=3;    //等价于 *(p2.operator *())=*(p2.operator *())+3; 
　　　　　　　　　　　　 //p2.operator *()返回一个int指针,并不会调用Point类的=操作符
    cout <<"*p2="<<*p2 <<endl;
    return 0;
}