将单目运算符"++"重载为成员函数形式

　　对于前置单目运算符，重载函数没有形参，对于后置单目运算符，重载函数有一个int型形参。这个int型参数在函数体中并不使用，纯粹是用来区别前置与后置，因此参数表中可以只给出类型名，没有参数名。

 1 #include <iostream>
 2 
 3 using namespace std;
 4 
 5 class Clock
 6 {
 7 public:
 8     Clock(int hour = 0,int min = 0,int sec = 0);
 9     void showTime();
10     Clock& operator++();    //前置单目运算符重载
11     Clock operator++(int);    //后置单目运算符重载
12 private:
13     int _hour;
14     int _min;
15     int _sec;
16 };
17 
18 Clock::Clock(int hour,int min,int sec)
19 {
20     if(0 <= hour && hour < 24
21                     && 0 <= min && min < 60
22                     && 0 <= sec && sec < 60)
23     {
24         _hour = hour;
25         _min = min;
26         _sec = sec;
27     }
28     else
29     {
30         cout << "Time Init error." << endl;
31     }
32 }
33 
34 void Clock::showTime()
35 {
36     cout << _hour << ":" << _min << ":" << _sec << endl;
37 }
38 
39 Clock& Clock::operator++()
40 {
41     std::cout << "Call front operator overloading" << std::endl;
42     _sec++;
43     if(_sec >= 60)
44     {
45         _sec = _sec - 60;
46         _min++;
47         if(_min >= 60)
48         {
49             _min = _min - 60;
50             _hour++;
51             _hour = _hour % 24;
52         }
53     }
54     return *this;
55 }
56 
57 Clock Clock::operator++(int)
58 {
59     std::cout << "Call post operator overloading" << std::endl;
60     Clock old = *this;
61     ++(*this);    //调用前置单目运算符重载函数
62     return old;
63 }
64 
65 int main(int argc,char* argv[])
66 {
67     Clock myClock(23,59,59);
68     cout << "current time: ";
69     myClock.showTime();
70     ++myClock;
71     cout << "++myClock: ";
72     myClock.showTime();
73     myClock++;
74     cout << "myClock++: ";
75     myClock.showTime();
76     return 0;
77 }

输出结果：

current time: 23:59:59

Call front operator overloading

++myClock: 0:0:0

Call post operator overloading

Call front operator overloading

myClock++: 0:0:1

 

posted @ 2021-03-07 15:54  阿玛尼迪迪  阅读(333)  评论(0)  编辑  收藏  举报