管理指针成员

来源：互联网发布：sqlite 创建数据库编辑：程序博客网时间：2024/06/06 15:50

void test_BHasPtr(){int obj = 0;BHasPtr ptr1(&obj, 45);BHasPtr ptr2(ptr1);cout << ptr1.get_ptr_val() << "," << ptr1.get_int() << endl;cout << ptr2.get_ptr_val() << "," << ptr2.get_int() << endl;cout << "修改以后" << endl;ptr2.set_ptr_val(2);ptr2.set_int(22);cout << ptr1.get_ptr_val() << "," << ptr1.get_int() << endl;cout << ptr2.get_ptr_val() << "," << ptr2.get_int() << endl;}

class AHasPtr{public:AHasPtr(int *p, int i) :ptr(p), val(i){}int *get_ptr() const { return ptr;}int get_int() const { return val;}void set_ptr(int *p) { ptr = p; }void set_int(int i)  { val = i; }int get_ptr_val() const{ return *ptr; }void set_ptr_val(int val)const { *ptr = val; }private:int val;int *ptr;};

/**********demo.cpp***********/

#include "iostream"#include "plain-ptr.h"using namespace std;void test_AHasPtr(){int i = 42;AHasPtr p1(&i, 30);AHasPtr p2 = p1;cout << p2.get_ptr_val() << endl;p1.set_ptr_val(0);cout << p2.get_ptr_val() << endl;/********野指针*********/int *ip = new int(40);AHasPtr ptr(ip, 10);cout << ptr.get_ptr_val() << endl;delete ip;/******野指针出现的一步*******/cout << ptr.get_ptr_val() << endl;}int main(){test_AHasPtr();return 0;}

出现的一大串数字就是悬垂指针。

复制构造函数不再复制一个指针。而是分配一个新的int对象并初始化该对象以保存与被复制对象相同的值。每个对象都保存属于自己的int值的不同副本，所以析构函数将不条件删除指针。

/*****深复制*****value-ptr.h**********/class CHasPtr{public:CHasPtr(const int &p, int i) :ptr(new int (p)), val(i){}CHasPtr(const CHasPtr &orig):ptr(new int(*orig.ptr)), val(orig.val){}CHasPtr& operator = (const CHasPtr&);~CHasPtr() { delete ptr; }int *get_ptr() const { return ptr; }int get_int() const { return val; }void set_ptr(int *p) { ptr = p; }void set_int(int i)  { val = i; }int get_ptr_val() const{ return *ptr; }void set_ptr_val(int val)const { *ptr = val; }private:int val;int *ptr;};CHasPtr& CHasPtr::operator=(const CHasPtr &rhs){*ptr = *rhs.ptr;val = rhs.val;return *this;}

void test_CHasPtr(){int obj = 0;CHasPtr ptr1(obj,42);CHasPtr ptr2(ptr1);cout << ptr1.get_ptr_val() << "," << ptr1.get_int() << endl;ptr2.set_ptr_val(6);ptr2.set_int(48);cout << "修改以后"<<endl;cout << ptr1.get_ptr_val() << "," << ptr1.get_int() << endl;cout << ptr2.get_ptr_val() << "," << ptr2.get_int() << endl;}

class U_Ptr{friend class BHasPtr;private:int *ip;size_t use;//计数U_Ptr(int *p) :ip(p), use(1){}~U_Ptr()  { delete ip; }};

class BHasPtr{public:BHasPtr(int *p, int i) :ptr(new U_Ptr(p)), val(i){}BHasPtr(const BHasPtr &orig) :ptr(orig.ptr), val(orig.val){++ptr->use;}BHasPtr& operator = (const BHasPtr&);~BHasPtr(){if (--ptr->use = 0)delete ptr;}int *get_ptr() const { return ptr->ip; }int get_int() const { return val; }void set_ptr(int *p) { ptr->ip = p; }void set_int(int i)  { val = i; }int get_ptr_val() const{ return *ptr->ip; }void set_ptr_val(int val)const { *ptr->ip = val; }private:int val;//int *ptr;U_Ptr *ptr;};BHasPtr& BHasPtr::operator=(const BHasPtr &rhs){++rhs.ptr->use;if (--ptr->use == 0)delete ptr;ptr = rhs.ptr;val =rhs.val;return *this;}

/****智能指针*********/void test_BHasPtr(){int obj = 0;BHasPtr ptr1(&obj, 45);BHasPtr ptr2(ptr1);cout << ptr1.get_ptr_val() << "," << ptr1.get_int() << endl;cout << ptr2.get_ptr_val() << "," << ptr2.get_int() << endl;cout << "修改以后" << endl;ptr2.set_ptr_val(2);ptr2.set_int(22);cout << ptr1.get_ptr_val() << "," << ptr1.get_int() << endl;cout << ptr2.get_ptr_val() << "," << ptr2.get_int() << endl;}

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