c++ - Class definition in a header c++

Question

I have this code:

#include <time.h> 
class ElapsedTime
{   
    time_t _startTime;
public:
    ElapsedTime(void){
        time(&_startTime);  
    }

    double MiliSecond()
    {
        time_t endTime;
        time(&endTime);
        return difftime(_startTime,endTime) * 1000;
    }

    ~ElapsedTime(void);
};

and I used it inside my c++ code. It compiles but generate error during linking as the linker says it can not find the elapsetime definition.

How can I define a class completely in an H file? For this simple class, I don't want to have a .h and a .cpp.

Answer 1

您忘记为析构函数提供定义：

~ElapsedTime(void) { }
//                 ^^^

但是请注意，在这种情况下您不需要显式提供析构函数：编译器将为您隐式生成一个析构函数。简单地省略它。

Answer 2

您缺少析构函数的实现：

~ElapsedTime() { ..... }

如果析构函数没有做任何事情，并且 is not virtual，您可以改为删除声明。