class Point                                       //基礎(chǔ)對象類
{
public:
     Point(int xVal = 0, int yVal = 0):x(xVal),y(yVal) { }
     int getX() const { return x; }
     int getY() const { return y; }
     void setX(int xVal) { x = xVal; }
     void setY(int yVal) { y = yVal; }

private:
     int x,y;
};
class RefPtr                                  //輔助類
{    //該類成員訪問權(quán)限全部為private，因?yàn)椴幌胱層脩糁苯邮褂迷擃?BR>     friend class SmartPtr;                                  //定義智能指針類為友元，因?yàn)橹悄苤羔橆愋枰苯硬倏v輔助類
     RefPtr(Point *ptr):p(ptr), count(1) { }
     ~RefPtr() { delete p; }
     int count;                                                     //引用計(jì)數(shù)
     Point *p;                                                      //基礎(chǔ)對象指針
};
class SmartPtr                                             //智能指針類
{
public:
     SmartPtr(Point *ptr):rp(new RefPtr(ptr)) { }                                 //構(gòu)造函數(shù)
     SmartPtr(const SmartPtr &sp):rp(sp.rp) { ++rp->count; }            //復(fù)制構(gòu)造函數(shù)
     SmartPtr& operator=(const SmartPtr& rhs) {                              //重載賦值操作符
     ++rhs.rp->count;                                                                        //首先將右操作數(shù)引用計(jì)數(shù)加1，
     if(--rp->count == 0)                                                                     //然后將引用計(jì)數(shù)減1，可以應(yīng)對自賦值
        delete rp;
     rp = rhs.rp;
     return *this;
     }
    ~SmartPtr() {                                            //析構(gòu)函數(shù)
    if(--rp->count == 0)                                  //當(dāng)引用計(jì)數(shù)減為0時(shí)，刪除輔助類對象指針，從而刪除基礎(chǔ)對象
         delete rp;
 }
private:
     RefPtr *rp;                                                //輔助類對象指針
};
int main()
{
     Point *p1 = new Point(10, 8);
     SmartPtr sp1(p1);
     SmartPtr sp2(sp1);
     Point *p2 = new Point(5, 5);
     SmartPtr sp3(p2);
     sp3 = sp1;
     return 0;
}

class Point                                                  //基礎(chǔ)對象類
{
public:
     Point(int xVal = 0, int yVal = 0):x(xVal),y(yVal) { }
     int getX() const { return x; }
     int getY() const { return y; }
     void setX(int xVal) { x = xVal; }
     void setY(int yVal) { y = yVal; }
public:
     virtual Point* clone() const {               //虛函數(shù)，為了實(shí)現(xiàn)讓句柄類在不知道對象的確切類型的情況下分配已知對象的新副本
     return new Point(*this);
 }

private:
     int x,y;
};
class D3Point : public Point                           //派生類
{
public:
     D3Point(int xVal, int yVal, int zVal):Point(xVal, yVal), z(zVal) { }
     int getZ() const { return z; }
     void setZ(int zVal) { z = zVal; }
public:
     D3Point* clone() const {                 //虛函數(shù)，為了實(shí)現(xiàn)讓句柄類在不知道對象的確切類型的情況下分配已知對象的新副本
  return new D3Point(*this);
 }
private:
     int z;
};
class SmartPtr
{
public:
     SmartPtr(Point *ptr = 0):p(ptr), count(new int(1)) { }                                         //構(gòu)造函數(shù)
     SmartPtr(Point &point):p(point.clone()), count(new int(1)) { }                          //構(gòu)造函數(shù)
     SmartPtr(const SmartPtr &sp):p(sp.p), count(sp.count) { ++*count; }             //復(fù)制構(gòu)造函數(shù)
     SmartPtr& operator=(const SmartPtr &sp) {                                                   //重載賦值操作符
         ++*sp.count;                                           //首先將右操作數(shù)引用計(jì)數(shù)加1，
         decr_use();                                             //然后將引用計(jì)數(shù)減1，可以應(yīng)對自賦值
         p = sp.p;
         count = sp.count;
         return *this;
     }
    ~SmartPtr() {                                          //析構(gòu)函數(shù)
          decr_use();
     }
public:                                   //一般情況下不會實(shí)現(xiàn)這兩個(gè)操作符，因?yàn)槲覀儾幌Ｍ脩糁苯硬倏v基礎(chǔ)對象指針
     const Point* operator->() const {
          if(p) return p;
          else throw logic_error("Unbound Point");
     }
 const Point& operator*() const {
      if(p) return *p;
      else throw logic_error("Unbound Point");
     }
private:
    void decr_use() {
        if(--*count == 0)
        {
             delete p;
             delete count;
       }
    }
private:
     Point *p;                                      //基礎(chǔ)對象指針
     int *count;                                   //指向引用計(jì)數(shù)的指針
};
int main()
{
      Point *p1 = new Point(10, 8);
      SmartPtr sp1(p1);
      SmartPtr sp2(sp1);
      D3Point *p2 = new D3Point(5, 5, 0);
      SmartPtr sp3(p2);
      return 0;
}