关于解引用*和箭头操作符->的重载

时间：2014-08-10 23:59:30 阅读：532 评论：0 收藏：0 [点我收藏+]

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这里以一个智能指针类为例，智能指针所指为一个对象。

而事实上，STL迭代器的开发均需要重载这两个操作符，上一篇文章分析STL 迭代器中除了要用到template技巧外，还需要重载技巧

 1 #include<iostream>
 2 using namespace std;
 3 class Screen
 4 {
 5     
 6 public:
 7     friend ostream& operator<<(ostream&os, Screen &s);
 8     int action(){ return ++data; }
 9     Screen(int i = 0) :data(i){}
10 private:
11     int data;
12 };
13 ostream& operator<<(ostream&os, Screen &s)
14 {
15     os << s.data;
16     return os;
17 }
18 class U_ptr
19 {
20     friend class ScreenPtr;
21     Screen* p;
22     size_t use;
23     U_ptr(Screen *pp) :p(pp), use(1){}
24     ~U_ptr(){ delete p; }
25 };
26 class ScreenPtr
27 {
28 private:
29     U_ptr *ptr;
30 public:
31     ScreenPtr(Screen *p) :ptr(new U_ptr(p)){}
32     ScreenPtr(ScreenPtr &orgi_p) :ptr(orgi_p.ptr){ ++ptr->use; }
33     ~ScreenPtr(){ if (--ptr->use == 0)delete ptr; }
34     Screen& operator*()
35     {
36         return *(ptr->p);
37     }
38     Screen* operator->()
39     {
40         return ptr->p;
41     }
42 };
43 class gao
44 {
45 private:
46     ScreenPtr *p;
47 public:
48     gao(ScreenPtr* q) :p(q){}
49     ScreenPtr& operator->()
50     {
51         return *p;
52     }
53 };
54 int main()
55 {
56     
57     ScreenPtr ptr(new Screen(5));
58     cout << "*操作符  " << *ptr << endl;
59     cout << "->操作符  " << ptr->action() << endl;
60     ScreenPtr* pp = &ptr;
61     gao d(pp);
62     cout << "!" << d->action() << endl;
63     system("pause");
64 }