以下是说明：
在第10章中，类clockType旨在在程序中实现一天中的时间。除小时，分钟和秒之外，某些应用程序可能还需要您存储时区。
从类extClockType中派生类clockType
通过添加成员变量来存储时区。添加必要的成员函数和构造函数以使类起作用。另外，编写成员函数和构造函数的定义。最后，编写一个测试程序来测试您的课程。
这是我的文件：
clockType.h
//clockType.h, the specification file for the class clockType
#ifndef H_ClockType
#define H_ClockType
class clockType
{
public:
void setTime(int hours, int minutes, int seconds);
//Function to set the time.
//The time is set according to the parameters.
//Postcondition: hr = hours; min = minutes;
// sec = seconds
// The function checks whether the values of
// hours, minutes, and seconds are valid. If a
// value is invalid, the default value 0 is
// assigned.
void getTime(int& hours, int& minutes, int& seconds) const;
//Function to return the time.
//Postcondition: hours = hr; minutes = min;
// seconds = sec
void printTime() const;
//Function to print the time.
//Postcondition: The time is printed in the form
// hh:mm:ss.
void incrementSeconds();
//Function to increment the time by one second.
//Postcondition: The time is incremented by one
// second.
// If the before-increment time is 23:59:59, the
// time is reset to 00:00:00.
void incrementMinutes();
//Function to increment the time by one minute.
//Postcondition: The time is incremented by one
// minute.
// If the before-increment time is 23:59:53,
// the time is reset to 00:00:53.
void incrementHours();
//Function to increment the time by one hour.
//Postcondition: The time is incremented by one
// hour.
// If the before-increment time is 23:45:53, the
// time is reset to 00:45:53.
bool equalTime(const clockType& otherClock) const;
//Function to compare the two times.
//Postcondition: Returns true if this time is
// equal to otherClock; otherwise,
// returns false.
clockType(int hours, int minutes, int seconds);
//constructor with parameters
//The time is set according to the parameters.
//Postcondition: hr = hours; min = minutes;
// sec = seconds
// The constructor checks whether the values of
// hours, minutes, and seconds are valid. If a
// value is invalid, the default value 0 is
// assigned.
clockType();
//default constructor with parameters
//The time is set to 00:00:00.
//Postcondition: hr = 0; min = 0; sec = 0
private:
int hr; //variable to store the hours
int min; //variable to store the minutes
int sec; //variable to store the seconds
};
#endif
clockTypeImp.cpp
//Implementation File for the class clockType
#include <iostream>
#include "clockType.h"
using namespace std;
void clockType::setTime(int hours, int minutes, int seconds)
{
if (0 <= hours && hours < 24)
hr = hours;
else
hr = 0;
if (0 <= minutes && minutes < 60)
min = minutes;
else
min = 0;
if (0 <= seconds && seconds < 60)
sec = seconds;
else
sec = 0;
}
void clockType::getTime(int& hours, int& minutes,
int& seconds) const
{
hours = hr;
minutes = min;
seconds = sec;
}
void clockType::incrementHours()
{
hr++;
if (hr > 23)
hr = 0;
}
void clockType::incrementMinutes()
{
min++;
if (min > 59)
{
min = 0;
incrementHours();
}
}
void clockType::incrementSeconds()
{
sec++;
if (sec > 59)
{
sec = 0;
incrementMinutes();
}
}
void clockType::printTime() const
{
if (hr < 10)
cout << "0";
cout << hr << ":";
if (min < 10)
cout << "0";
cout << min << ":";
if (sec < 10)
cout << "0";
cout << sec;
}
bool clockType::equalTime(const clockType& otherClock) const
{
return (hr == otherClock.hr
&& min == otherClock.min
&& sec == otherClock.sec);
}
clockType::clockType(int hours, int minutes, int seconds)
{
if (0 <= hours && hours < 24)
hr = hours;
else
hr = 0;
if (0 <= minutes && minutes < 60)
min = minutes;
else
min = 0;
if (0 <= seconds && seconds < 60)
sec = seconds;
else
sec = 0;
}
clockType::clockType() //default constructor
{
hr = 0;
min = 0;
sec = 0;
}
（给出了前两个文件）
（从这里开始创建代码）
extClockType.h
#ifndef H_extClockType
#define H_extClockType
#include<iostream>
#include "clockType.h"
using namespace std;
class extClockType: public clockType
{
public:
extClockType();
extClockType(int, int, int, string);
void setTime(int hours, int minutes, int seconds, string zone);
string printTimezone();
string getTimezone();
private:
string zone;
};
#endif
extClockTypeImp.cpp
#include <iostream>
#include "clockType.h"
#include "extClockType.h"
using namespace std;
extClockType::extClockType(): clockType()
{
zone = "na";
}
extClockType::extClockType(int hours, int minutes, int seconds, string time_zone)
{
clockType::setTime(hours, minutes, seconds);
zone = time_zone;
}
void extClockType::setTime(int hours, int minutes, int seconds, string zone)
{
clockType::setTime(hours, minutes, seconds);
}
string extClockType::getTimezone()
{
return zone;
}
string extClockType::printTimezone()
{
clockType::printTime();
cout << " " << zone << endl;
return 0;
}
main.cpp
#include <string>
#include <iomanip>
#include <iostream>
#include "clockType.h"
#include "extClockType.h"
using namespace std;
int main()
{
extClockType time1(5, 10, 34, "CST");
cout << "Time 1: ";
time1.printTimezone();
cout<<endl;
extClockType time2;
time2.setTime(12, 45, 59, "PST");
cout<< "Time 2: ";
time2.printTimezone();
cout<<endl;
time2.incrementSeconds();
cout<< "After incrementing time 2 by one second, Time 2:";
time2.printTime();
}
这是我的错误消息：
Time 1: 05:10:34 CST
terminate called after throwing an instance of 'std::logic_error'
what(): basic_string::_M_construct null not valid
很抱歉，我发布的帖子太长了，我只想显示我正在使用的所有文件。如果有人愿意帮助我，那将是巨大的帮助！
答案 0 :(得分：3)
该错误仅表示您已调用了字符串构造函数：
std::string::string(const char *p);
使用NULL指针，这不是一件有效的事情。
使用调试器准确地找出 您的代码在何处执行此操作，并将其修复为不执行此操作。
答案 1 :(得分：1)
这是一个错误：
string extClockType::printTimezone()
{
clockType::printTime();
cout << " " << zone << endl;
return 0; // This is not legal, converting an int to a std::string
}
返回时，您将返回0，并且正在尝试将其转换为std::string。 std::string的构造函数没有采用int参数（在这种情况下为0）。而是会引发异常。
您应该不返回任何内容（因此应将函数声明为返回void），或者返回可以创建有效std::string的内容。
注意：为std::string调用的构造函数是采用单个const char *自变量(see constructor (5))的构造函数。在这种情况下，0会转换为nullptr，因此在返回时会尝试构建std::string(nullptr)。
答案 2 :(得分：0)
毕竟容易
string extClockType::printTimezone() {
...
return 0;
}
将其更改为此并更新原型：
void extClockType::printTimezone() {
...
return;
}
这试图构造一个0的std :: string解释为nullptr。根据用法，返回值可能应该为空。
修复后，输出为：
时间1：05：10：34 CST
时间2：12：45：59不适用
将时间2递增一秒后，时间2：12：46：00
请注意，“ na”是
的结果void setTime(int hours, int minutes, int seconds, string zone);
实际上没有设置“ zone”成员变量。