Question

我一直在尝试创建一个类笛卡尔，其中对象是笛卡尔点上的2个点（int或double）。然后我想重载＆lt;＆lt;。我收到错误消息：

Undefined symbols for architecture x86_64:
  "cartesian<double, int>::cartesian(double, int)", referenced from:
      _main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

我不明白我的错误在哪里。

THE HEADER

#include <iostream>    

using namespace std;

template <class first, class second>
class cartesian
{

public:
    cartesian(first, second);

    //double getslope(cartesian &obj1, cartesian &obj2);

    friend ostream& operator<< (ostream &out, cartesian &cPoint);                

private:
    first x;
    second y;

};

CPP文件

#include "cartesian.h"
#include <iostream>

using namespace std;


template<class first,class second>

cartesian<first, second>::cartesian(first a, second b)
:x(a), y(b)
{}

/*
// between obj1 and obj2
template<class first,class second>
double cartesian<first, second>::getslope(cartesian &obj1, cartesian &obj2){

    return ((obj2.y-obj1.y)/(obj2.x-obj1.y));
}

*/


template<class first,class second>

ostream&  operator<< (ostream &out,const cartesian<first, second> &cPoint)
{
    // Since operator<< is a friend of the Point class, we can access
    // Point's members directly.
    out << "(" << cPoint.x << ", " <<
    cPoint.y << ")";

    return out;
}

主要

#include <iostream>
#include "cartesian.h"

using namespace std;

int main()
{

    cartesian<double, int> ob11(3.4, 6);
    return 0;
}

Answer 1

您需要将实现放在头文件或标头包含的文件中。编译器需要访问代码才能在cartesian<double, int>中“构建”您需要的main专业化。

例如，这里我们将构造函数的实现放在类声明中：

template <class first, class second>
class cartesian
{

public:
    cartesian(first, second) :x(a), y(b) {}
};

它不必进入类声明本身，但必须可以从头文件中访问代码。

类模板链接器错误

1 个答案: