C++的类、操作符重载与派生类

1、 类的基本概念

定义一个时间类，它能表示时、分、秒，并提供以下操作。编写程序测试类的功能。

• (1)Time (int h, int m, int s);//构造函数
• (2) Time (Time const &x) //拷贝构造函数
• (3) void set(int h, int m, int s);//设置时间
• (4)Time & increment();//自动加1秒
• (5)void display( );//显示时间
• (6)bool equal(Time const & x);//判断两个时间是否相等
• (7)bool less_than(Time const &x);//比较两个时间大小

2、 操作符重载函数

为Time类继续添加以下成员函数,并测试

• (1) 赋值操作符重载函数    Time & operator = (Time const &x)
• (2) 类型转换函数//将时间转换为秒数        operator int( )
• (3) 可用作类型转换的构造函数   Time ( int ) //将int类型转换为Time格式，如Time(60)为0:1:0
• (4) 时间的比较 bool operator = = (Time const & x); bool operator < (Time const & x)
• (5) 增加/减少若干秒  Time operator + (int n) ; Time operator – (int n)
• (6) 增加/减少1秒     Time & operator ++( ) ; Time& operator – -( )
• (7) 计算两个时刻相差的秒数。int operator- ( Time const &x);

3、 派生类

利用时间类Time，定义一个带时区的时间类ExtTime。除了构造函数和时间调整函数外，ExtTime的其他功能与Time类似。用虚函数实现函数void display( );调用的动态绑定。

实现：

头文件time.h

#ifndef TIME_H#define TIME_H#include <string>class Time{int hour;int minute;int second;// 判断时间是否正确bool test_Time(int h, int m, int s);public:// 构造函数Time();Time(int h, int m, int s);Time(Time const &x);Time(int s);// 操作函数void set(int h, int m, int s);Time & increment();virtual void display();bool equal(Time const &x);bool less_than(Time const &x);// 操作符重载Time & operator = (Time const &x);operator int();bool operator == (Time const &x);bool operator < (Time const &x);Time operator + (int n);Time operator - (int n);Time & operator ++ ();Time & operator -- ();int operator - (Time const &x);};// 派生类class extTime :public Time{std::string address;public:// 构造函数extTime();extTime(const std::string &a, int h, int m, int s);extTime(const std::string &a, Time const &x);extTime(extTime const &x);//操作函数void set(const std::string &a, int h, int m, int s);void display();};#endif

类与派生类的实现time.cpp

#include <iostream>#include "time.h"bool Time::test_Time(int h, int m, int s){if (h <= 24 && h >= 0 && m <= 60 && m >= 0 && s <= 60 && s >= 0)return true;elsereturn false;}Time::Time(){hour = minute = second = 0;}Time::Time(int h, int m, int s){hour = h;minute = m;second = s;}Time::Time(Time const &x){hour = x.hour;minute = x.minute;second = x.second;}Time::Time(int s){second = s % 60;minute = (s / 60) % 60;hour = s / 3600;}void Time::set(int h, int m, int s) {if (test_Time(h, m, s)) {hour = h;minute = m;second = s;}else {std::cout << "The time you set is incorrect! Please set again." << std::endl;}}Time & Time::increment() {if (second == 60 && minute < 60) {minute++;second = 0;}else if (second == 60 && minute == 60) {hour++;minute = second = 0;}else {second++;}return *this;}void Time::display() {std::cout << hour << ":" << minute << ":" << second << std::endl;}bool Time::equal(Time const &x) {return ((hour == x.hour)&(minute == x.minute)&(second == x.second));}bool Time::less_than(Time const &x){if ((hour * 3600 + minute * 60 + second) < (x.hour * 3600 + x.minute * 60 + x.second))return true;elsereturn false;}Time & Time::operator = (Time const &x){//防止自身赋值if (&x == this)return *this;hour = x.hour;minute = x.minute;second = x.second;return *this;}Time::operator int(){return (hour * 3600 + minute * 60 + second);}bool Time::operator == (Time const &x){return ((hour == x.hour)&(minute == x.minute)&(second == x.second));}bool Time::operator < (Time const &x){if ((hour * 3600 + minute * 60 + second) < (x.hour * 3600 + x.minute * 60 + x.second))return true;elsereturn false;}Time Time::operator + (int n){int temp1 = (int)*this + n;Time temp2(temp1);return temp2;}Time Time::operator - (int n){int temp1 = (int)*this - n;Time temp2(temp1);return temp2;}Time & Time::operator ++ (){int temp1 = (int)*this;temp1 ++;Time temp2(temp1);*this = temp2;return *this;}Time & Time::operator -- (){int temp1 = (int)*this;temp1 --;Time temp2(temp1);*this = temp2;return *this;}int Time::operator - (Time const &x){Time temp;temp = x;return (int)*this - (int)temp;}extTime::extTime() :Time(){address = "BeiJing";}extTime::extTime(const std::string &a, int h, int m, int s) : Time(h, m, s){address = a;}extTime::extTime(const std::string &a, Time const &x):Time(x){address = a;}extTime::extTime(extTime const &x) : Time(x){address = x.address;}void extTime::set(const std::string &a, int h, int m, int s){Time::set(h, m, s);address = a;}void extTime::display(){std::cout << address << "-";Time::display();}

测试文件testClass.cpp

// 测试类Time的正确性#include <iostream>#include "time.h"int main(){using std::cout;using std::endl;Time T1(11, 11, 11);cout << "时间T1：";T1.display();Time T2(T1);cout << "时间T2：";T2.display();T1.set(11, 11, 60);cout << "设置时间T1：";T1.display();T1 = T1.increment();cout << "时间T1自动加1秒：";T1.display();cout << "T1与T2是否相等？ ";cout << T1.equal(T2) << endl;cout << "T1是否小于T2？ ";cout << T1.less_than(T2) << endl;// 测试赋值操作符重载函数T1 = T2;// 测试类型转换函数int i = 1;int z = i + T1;cout << "z = " << z << endl;// 测试可用作类型转换的构造函数Time T3(66);cout << "时间T3：";T3.display();// 测试比较运算符重载函数cout << "T3 == T1? " << (T3 == T1) << endl;cout << "T3 < T1? " << (T3 < T1) << endl;// 测试增加减少若干秒T3 = T3 + 88;cout << "T3增加88秒为：";T3.display();T3 = T3 - 88;cout << "T3减少88秒为：";T3.display();// 测试增加较少一秒++T3;cout << "T3增加1秒为：";T3.display();--T3;cout << "T3减少一秒为：";T3.display();// 测试计算两个时刻相差秒数cout << "T1与T3相差秒数：";int difference = (T1 - T3);cout << difference << endl;// 测试派生类的构造函数extTime T4;T4.display();extTime T5("NewYork", 6, 7, 8);T5.display();extTime T6("BeiJing", T2);T6.display();extTime T7(T6);T7.display();T7.set("Tokyo", 14, 15, 16);T7.display();// 测试虚函数行为Time *testVirtual;testVirtual = &T2;testVirtual->display();testVirtual = &T5;testVirtual->display();getchar();return 0;}