在引发'std::logic_error‘what()：basic_string::_M_construct null无效实例后调用的终止
在引发'std::logic_error‘what()：basic_string::_M_construct null无效实例后调用的终止
提问于 2018-09-02 22:36:26
以下是说明：
在第10章中，clockType类被设计成在程序中实现一天中的时间。某些应用程序，除了小时、分钟和秒外，可能需要存储时区。
通过添加一个成员变量来存储时区，从类extClockType派生类clockType。添加必要的成员函数和构造函数，以使类具有功能。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。
这是我的档案：
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
};
#endifclockTypeImp.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，我创建代码)
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;
};
#endifextClockTypeImp.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
很抱歉我的帖子太长了，我只想展示我正在处理的所有文件。如果有人愿意帮助我，那将是一个巨大的帮助！
回答 3
Stack Overflow用户
发布于 2018-09-02 23:16:06
此错误只意味着您已经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。
使用调试器可以找出代码的确切位置，并将其修复为不这样做。
Stack Overflow用户
发布于 2018-09-02 23:18:09
一个错误是：
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没有接受int参数的构造函数(在本例中为0)。相反，将引发异常。
您应该不返回任何内容(因此函数应该声明为返回void)，或者返回一些创建有效std::string的内容。
注意:为std::string调用的构造函数是接受单个const char *参数(见构造函数(5))的构造函数。在这种情况下，0被转换为nullptr，因此在返回时尝试构造一个std::string(nullptr)。
Stack Overflow用户
发布于 2018-09-02 23:21:25
毕竟很容易
string extClockType::printTimezone() {
...
return 0;
}将其更改为此，并更新原型：
void extClockType::printTimezone() {
...
return;
}这将尝试构造带有0的std::string，将其解释为nullptr。根据使用情况，返回值可能为空。
修复后，输出如下：
时间1: 05:10:34科技委
时间2: 12:45:59 na
增加时间2秒后，时间2:12:46:00
请注意，“na”是
void setTime(int hours, int minutes, int seconds, string zone);实际上没有设置“zone”成员变量。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/52141476
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