singleton question

From:

kathy <yqin_99@yahoo.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 24 Feb 2011 07:23:45 -0800 (PST)

Message-ID:

<95dd062d-415f-44e3-bcbd-b79ed10f7513@8g2000prt.googlegroups.com>

I try to implement the Singleton for my Driver. The code piece:

/////////////////////////
MySingleton.h
/////////////////////////
template <class T> class CSingleton
{
public:
  static T* GetInstance();

protected:
  CSingleton();
  ~CSingleton();

private:
  CSingleton(CSingleton const&);
  CSingleton& operator=(CSingleton const&);
  static T* m_pInstance;
};

/////////////////////////
MySingleton.cpp
/////////////////////////

#include "StdAfx.h"
#include "MySingleton.h"

template <class T> T* CSingleton<T>::m_pInstance=NULL;
template <class T> T* CSingleton<T>::GetInstance()
{
  if(!m_pInstance)
    m_pInstance = new T;

  assert(m_pInstance !=NULL);

  return m_pInstance;
}

/////////////////////////
Driver.h
/////////////////////////

class CDriver
{
public:
    CDriver(void);
    ~CDriver(void);

    int GetData();

private:
    int m_nData;
};

/////////////////////////
Driver.cpp
/////////////////////////

#include "StdAfx.h"
#include "Driver.h"

CDriver::CDriver(void):
    m_nData(100)
{
}

CDriver::~CDriver(void)
{
}

int CDriver::GetData()
{
    return m_nData;
}

In my MFC dialog button routine:

void CMyDlg::OnBnClickedButtonSingleton()
{
    int n = 1;
    CDriver *pDriver = CSingleton<CDriver>::GetInstance();
    n = pDriver->GetData();
}

When I try to build it in studio 2010, I got link error:

MyDlg.obj : error LNK2019: unresolved external symbol "public: static
class CDriver * __cdecl CSingleton<class
CDriver>::GetInstance(void)" (?GetInstance@?
$CSingleton@VCDriver@@@@SAPAVCDriver@@XZ) referenced in function
"public: void __thiscall
CBoostDlg::OnBnClickedButtonSingleton(void)" (?
OnBnClickedButtonSingleton@CBoostDlg@@QAEXXZ)
C:\Temp\Studio 2010\TestDlg\Debug\Test.exe : fatal error LNK1120: 1
unresolved externals

What is wrong?