Question

我已阅读很多关于LNK2019的帖子，但无法解决此错误。

这是我的代码：

time.h中：

#ifndef PROJECT2_TIME_H
#define PROJECT2_TIME_H

#include<iostream>
using std::ostream;

namespace Project2  
{
class Time
{
    friend Time& operator+=(const Time& lhs, const Time& rhs);
    friend ostream& operator<<(ostream& os, const Time& rhs);
public:
    static const unsigned secondsInOneHour = 3600;
    static const unsigned secondsInOneMinute = 60;
    Time(unsigned hours, unsigned minutes, unsigned seconds);
    unsigned getTotalTimeAsSeconds() const;
private:
    unsigned seconds;
};

Time& operator+=(const Time& lhs, const Time& rhs);
ostream& operator<<(ostream& os, const Time& rhs);

}

#endif

Time.cpp：

#include "Time.h"


Project2::Time::Time(unsigned hours, unsigned minutes, unsigned seconds)   
{
    this->seconds = hours*secondsInOneHour + minutes*secondsInOneMinute + seconds;
}

unsigned
Project2::Time::getTotalTimeAsSeconds() const
{
return this->seconds;
}


Project2::Time&
Project2::operator+=(const Time& lhs, const Time& rhs)
{
Time& tempTime(unsigned hours, unsigned minutes, unsigned seconds);
unsigned lhsHours = lhs.seconds / Time::secondsInOneHour;
unsigned lhsMinutes = (lhs.seconds / 60) % 60;
unsigned lhsSeconds = (lhs.seconds / 60 / 60) % 60;
unsigned rhsHours = rhs.seconds / Time::secondsInOneHour;
unsigned rhsMinutes = (rhs.seconds / 60) % 60;
unsigned rhsSeconds = (rhs.seconds / 60 / 60) % 60;
return tempTime(lhsHours + rhsHours, lhsMinutes + rhsMinutes, lhsSeconds + rhsSeconds);
}

ostream&
Project2::operator<<(ostream& os, const Time& rhs)
{
unsigned rhsHours = rhs.seconds / Time::secondsInOneHour;
unsigned rhsMinutes = (rhs.seconds / 60) % 60;
unsigned rhsSeconds = (rhs.seconds / 60 / 60) % 60;
os << rhsHours << "h:" << rhsMinutes << "m:" << rhsSeconds << "s";
return os;
}

main.cpp只是简单地创建Time对象并使用重载的运算符，似乎不存在问题（提供这些代码本身就是好的）。

我试图删除“＆amp;”在所有“时间”符号后面，我得到了同样的错误。

以下是错误消息：

错误1错误LNK2019：未解析的外部符号“类Project2 :: Time＆amp; __cdecl tempTime（unsigned int，unsigned int，unsigned int）”（？tempTime @@ YAAAVTime @ Project2 @@ III @ Z）在函数中引用“ class Project2 :: Time＆amp; __cdecl Project2 :: operator + =（class project2 :: Time const＆amp;，class Project2 :: Time const＆amp;）“（?? YProject2 @@ YAAAVTime @ 0 @ ABV10 @ 0 @ Z）c ：\ Users \ Eon-Gwei \ documents \ visual studio 2013 \ Projects \ c ++ III_Project2_GW \ c ++ III_Project2_GW \ Time.obj c ++ III_Project2_GW

Answer 1

Time& tempTime(unsigned hours, unsigned minutes, unsigned seconds);声明一个名为tempTime的函数，并return tempTime(lhsHours + rhsHours, lhsMinutes + rhsMinutes, lhsSeconds + rhsSeconds);调用该函数。由于该函数在任何地方都没有实现，因此会出现链接器错误。

~~由于operator +=可能会返回对其调用对象的引用，因此您应该通过this修改对象的成员变量，而不是创建新的Time {1}}，并返回*this。~~ 编辑：任何理智的operator +=实现都会修改左侧操作数，而不是创建新对象。我建议你重新考虑一下你的运营商应该如何运作。

C ++ LNK2019未解析的外部符号

1 个答案: