singleton class.

[JohnChen]

#ifndef SC_H
#define SC_H



class SC
{
public:
~SC();

static SC* Get();

int GetNumber();
void SetNumber(int n);


protected:

SC();
static SC* s_Instance;

int m_Number;

};
//====================================================================================================
// Global Functions
//====================================================================================================

static SC* SCL( void )
{
return SC::Get();
}


;
#endif


// .cpp file


#include "stdafx.h"
#include "SingletonClass.h"


SC::~SC()
{
s_Instance = 0;
};

SC* SC::Get()
{
if (s_Instance == 0)
{
s_Instance = new SC();
}
return s_Instance;
};

int SC::GetNumber()
{
return m_Number;
};
void SC::SetNumber(int n)
{
m_Number = n;
};



SC::SC(): m_Number(0)

{s_Instance = 0;};

//errors:
Error 1 error LNK2020: unresolved token (0A00000F) "protected: static class SC * SC::s_Instance" (?s_Instance@SC@@1PAV1@A) SingletonClass.obj
Error 2 error LNK2001: unresolved external symbol "protected: static class SC * SC::s_Instance" (?s_Instance@SC@@1PAV1@A) SingletonClass.obj

How to solve this problem and where is wrong?

[guestgulkan]

protected: 

SC();
static SC* s_Instance; //This static variable must be initialised  outside the class declaration

int m_Number;

So somewhere in the CPP file put:
SC* SC::s_Instance=0;

[JohnChen]

Thanks.