未定义的静态成员变量引用 [英] undefined reference to static member variable
问题描述
我有这个类有一个静态成员。它也是我的程序中几个其他类的基类。这是它的头文件:
I have this class that has a static member. it is also a base class for several other classes in my program. Here's its header file:
#ifndef YARL_OBJECT_HPP
#define YARL_OBJECT_HPP
namespace yarlObject
{
class YarlObject
{
// Member Variables
private:
static int nextID; // keeps track of the next ID number to be used
int ID; // the identifier for a specific object
// Member Functions
public:
YarlObject(): ID(++nextID) {}
virtual ~YarlObject() {}
int getID() const {return ID;}
};
}
#endif
这里是它的实现文件。
and here's its implementation file.
#include "YarlObject.hpp"
namespace yarlObject
{
int YarlObject::nextID = 0;
}
我使用g ++,它返回三个未定义的引用'yarlObject :: YarlObject :: nextID
链接器错误。如果我将构造函数中的 ++ nextID
短语改为 nextID
,那么我只得到一个错误,如果我将其更改为 1
,然后它正确链接。
I'm using g++, and it returns three undefined reference to 'yarlObject::YarlObject::nextID
linker errors. If I change the ++nextID
phrase in the constructor to just nextID
, then I only get one error, and if I change it to 1
, then it links correctly. I imagine it's something simple, but what's going on?
推荐答案
确保您正在连接生成的.o文件。仔细检查makefile。
Make sure you are linking against the generated .o file. Double-check the makefile.
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