Question

我是C ++和面向对象编程的新手，所以请耐心等待这个问题。我正在编写一个日期程序，用于确定您输入的日期是否为闰年，计算两个日期之间的长度等。这是我的代码。它有一个头文件Date.h，以及两个源文件Date.cpp和main.cpp：

Date.h

#include <iostream>
using namespace std;
class Date {
private:
static const int month_nb;
static const unsigned char month_days[];
static const unsigned char month_daysLeap[];
protected:
static bool testLeap(const int year_);
bool isLeap;
int year;
int month;
int day;
public:


Date(const int month_,const int day_,const int year_);


~Date(){};


int get_month() const {return month;}
int get_day() const {return day;}
int get_year() const {return year;}


void set_month(int m){month = m;}
void set_day(int d){day = d;}
void set_year(int y){year = y;}


bool testLeap() const;
void out() const;
bool testValid() const;
int operator-(const Date & date) const;
static int Julian(const Date & date1,const Date & date2);
static double CountACT_365(const Date & date1,const Date & date2);
static int Count30_360L(const Date & date1,const Date & date2);
static double Count30_360(const Date & date1,const Date & date2);
double CountACT_365(const Date & date) const;
int Count30_360L(const Date & date) const;
double Count30_360(const Date & date) const;
};
inline bool operator==(const Date& d1,const Date& d2)
{
return d1.get_month()==d2.get_month()
&& d1.get_day()==d2.get_day() && d1.get_year()==d2.get_year();
}
ostream& operator<<(ostream& os,const Date& d);

Date.cpp

#include <iostream>
#include "Date.h"
using namespace std;
const int Date::month_nb = 12;
const unsigned char Date::month_days[] = {31,28,31,30,31,30,31,31,30,31,30,31};
const unsigned char Date::month_daysLeap[] = {31,29,31,30,31,30,31,31,30,31,30,31};
Date::Date(const int month_, const int day_, const int year_)
{
year = year_; month = month_; day = day_;
isLeap = testLeap();
}
bool Date::testLeap(const int year_)
{
//if the year is not a multiple of 4, this is not a leap year
if(year_ % 4 != 0) return false;
//if the year is a multiple of 100, this is not a leap year,
//except if it is a multiple of 400.
if(year_ % 100 == 0) {
return year_ % 400 == 0;
}
return true;
}
bool Date::testLeap() const {
return testLeap(year);
}
void Date::out() const
{
cout << (int)month <<"/"<< (int)day <<"/"<< year << endl;
}
bool Date::testValid() const {
return (1 <= month && month <= month_nb && 1 <= day
&& ((isLeap && day <= month_daysLeap[month-1])
|| (!isLeap && day <= month_days[month-1])));
}
ostream& operator<<(ostream& os,const Date& d) {
return os<<d.get_month()<<'/'<<d.get_day()<<'/'<<d.get_year();
}

的main.cpp

 #include <iostream>
#include "Date.h"
using namespace std;
int Count30_360L(Date date1, Date date2) {
return 360 * (int) (date2.get_year() - date1.get_year())
+ 30 * (int) (date2.get_month() - date1.get_month())
+ (date2.get_day() - date1.get_day());
}
double Count30_360(Date date1, Date date2) {
return (double) Count30_360L(date1, date2) / 360.0;
}
int main() {

    Date SBday = Date(8,24,1971);
    Date CBday = Date(9,28,1996);
    cout <<"Time elapsed " << CBday - SBday<<endl;
    cout << "Q: was 8/24/1971 in a leap year? A: "<<SBday.testLeap()<<endl;
    cout <<"Count30_360L(SBday,CBday) = "<< Count30_360L(SBday,CBday)<<endl;
    cout <<"Count30_360(SBday,CBday) = "<< Count30_360(SBday,CBday)<<endl;
    cout <<"CountACT_365(SBday,CBday) = "<< Count30_360L(SBday,CBday)<<endl;
    cout <<"CBday.Count30_360L(SBday) = "<< CBday.Count30_360L(SBday)<<endl;
    cout <<"CBday.Count30_360(SBday) = "<< CBday.Count30_360(SBday)<<endl;
    return 0;
    }

我收到以下错误消息：

g ++ -static-libgcc -static-libstdc ++ -o HW1_2.exe main.o Date.o

main.o：在函数`main'中：

... Debug /../ main.cpp：24：未定义引用`Date :: operator-（Date const＆amp;）const'

... Debug /../ main.cpp：29：未定义引用`Date :: Count30_360L（Date const＆amp;）const'

... Debug /../ main.cpp：30：未定义引用`Date :: Count30_360（Date const＆amp;）const'

有人可以帮帮我吗？谢谢！

Answer 1

... Debug /../ main.cpp：24：未定义引用`Date :: operator-（Date const＆amp;）const'

您在Date.h中声明了int operator-(const Date & date) const;但从未对其进行过定义。

... Debug /../ main.cpp：29：未定义引用`Date :: Count30_360L（Date const＆amp;）const'

您声明了int Count30_360L(const Date & date) const;但没有定义它（您确实定义了一个自由函数int Count30_360L(Date date1, Date date2)）。

... Debug /../ main.cpp：30：未定义引用`Date :: Count30_360（Date const＆amp;）const'

同样，你在Data.h中声明了double Count30_360(const Date & date) const;但从未定义它（但确实定义了一个自由函数double Count30_360(Date date1, Date date2)）。

这些功能都在main()中引用：

Bday - SBday
CBday.Count30_360L(SBday)
CBday.Count30_360(SBday)

您需要定义这些Date::成员函数（在Date.cpp中）。

此外：

using namespace std;

这在头文件中不是一个好主意。请参阅Why is "using namespace std" considered bad practice?

如果您缩进代码，这对于可读性也有很大帮助。

对class :: function错误的未定义引用

1 个答案: