81.类成员函数指针高级

 1 #include <iostream>
 2 using namespace std;
 3 
 4 //myclass类
 5 class myclass
 6 {
 7 public:
 8     int add(int a, int b)
 9     {
10         return a + b;
11     }
12     int sub(int a, int b)
13     {
14         return a - b;
15     }
16     int mul(int a, int b)
17     {
18         return a * b;
19     }
20     int divv(int a, int b)
21     {
22         return a / b;
23     }
24 };
25 
26 //类成员函数当做引用参数
27 void change(int(myclass::*&p)(int, int))
28 {
29     p = &myclass::sub;
30 }
31 
32 //changeit的参数是类成员函数指针的引用,返回值是类成员函数指针的引用
33 //类成员函数指针作为参数退化为二级类成员函数指针
34 int(myclass::*&  changit(  int(myclass::* &p)(int, int)  )  )(int, int)
35 {
36     p = &myclass::sub;
37     return p;
38 }
39 
40 void main()
41 {
42     myclass *pclass(nullptr);//空指针
43     //int(myclass::*p)(int, int) = &myclass::add;//类成员函数指针
44     //cout << pclass->add(1, 2) << endl;
45     //cout << (pclass->*p)(2, 3) << endl;
46     int(myclass::*p[4])(int, int) { &myclass::add, &myclass::sub, &myclass::mul, &myclass::divv };
47     //下标方式循环
48     for (int i = 0; i < 4; i++)
49     {
50         //调用类成员函数数组
51         cout << (pclass->*p[i])(100, 10) << endl;
52     }
53 
54     //指针方式循环(二级类成员函数指针遍历类成员函数指针)
55     for (int(myclass::**pp)(int, int) = p; pp < p + 4; pp++)
56     {
57         cout << (pclass->**pp)(100, 10) << endl;
58     }
59 
60     //在堆上创建类成员函数指针
61     int (myclass::**p2)(int,int) = new (int(myclass::*[4])(int,int)){ &myclass::add, &myclass::sub, &myclass::mul, &myclass::divv };
62     for (int i = 0; i < 4; i++)
63     {
64         //调用类成员函数数组
65         cout << (pclass->*p2[i])(100, 10) << endl;
66     }
67 
68     int(myclass::*p3)(int, int) = &myclass::add;
69     change(p3);
70     (pclass->*p3)(12, 2);
71     cin.get();
72 }