智能指针

 

/*
用计数器count，模拟基本的智能指针
在这里我定义，作为源的指针叫源指针，然后源指针的第一份copy叫父指针，父指针的copy叫子指针
*/


#include <iostream>
using namespace std;

class SmartPointer    //父指针类，
{
public:
    friend class Invoke;
public:
    int* sptr;    
    int count;    
    SmartPointer(int *ptr):sptr(ptr),count(1){}
    ~SmartPointer()
    {
        cout<<"SmartPointer destructor.\n";
        //delete sptr;    //do not!　　because you know.
     }
};

class Invoke
{
private:
    SmartPointer *iptr;　　//Invoke的指针是指向SmartPointer类的指针

    Invoke(){}
public:
    Invoke(int *ptr):iptr(new SmartPointer(ptr)){}
    Invoke(const Invoke &invoke)
    {
        invoke.iptr->count++;  //父指针计数器+1      
        iptr = invoke.iptr;
    }
    ~Invoke()
    {
        iptr->count--;
        if((iptr->count)==0)//析构函数调用一次，count--，当count==0的时候，才删除SmartPointer对象，即父指针
        {
　　　　　　　　cout<<"As COUNT increase to 0 ,we delete SmartPoint's object.\n";
             delete iptr;
        }
    }
    void show()
    {
        cout<<"this:"<<iptr
            <<".\t it includes "<<iptr->sptr
            <<"(counts "<<iptr->count
            <<",values "<<*iptr->sptr<<")."<<endl;
    }
};

int main()
{
    int data = 100;
    int *pointer = &data;//源指针
    Invoke test(pointer);//父指针
        test.show();

    Invoke test2 = test;//子指针
        test2.show();

    Invoke test3 = test;//子指针
        test3.show();
    test3.~Invoke();//count--
        test3.show();
    return 0;
}

 thats it.结果如下：