以下是说明:
在第10章中，clockType类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extClockType类派生clockType类
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类(class)。
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)
(从这里开始是我创建代码的地方)
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();
}
这是我的错误信息:
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，发布的时间太长，我只想显示我正在使用的所有文件。如果有人愿意尝试帮助我，那将是巨大的帮助!
最佳答案
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，这不是有效的操作。使用调试器找出您的代码执行此操作的确切位置，并将其修复为不执行此操作。