Singleton pattern in C++

Question

I have a question about the singleton pattern.

I saw two cases concerning the static member in the singleton class.

First it is an object, like this

Answer 1

A better approach is to create a singleton class. This also avoids the instance availability check in the GetInstance() function. This can be achieved using a function pointer.

class TSingleton;

typedef TSingleton* (*FuncPtr) (void);

class TSingleton {

TSingleton(); //prevent public object creation
TSingleton  (const TSingleton& pObject); // prevent copying object
static TSingleton* vObject; // single object of a class

static TSingleton* CreateInstance   (void);
static TSingleton* Instance     (void);
public:

static FuncPtr  GetInstance; 
};


FuncPtr TSingleton::GetInstance = CreateInstance;
TSingleton* TSingleton::vObject;

TSingleton::TSingleton()
{
}

TSingleton::TSingleton(const TSingleton& pObject)
{
}

TSingleton* TSingleton::CreateInstance(void)
{
if(vObject == NULL){

    // Introduce here some code for taking lock for thread safe creation
    //...
    //...
    //...

    if(vObject == NULL){

        vObject = new TSingleton();
        GetInstance = Instance;
    }
}

return vObject;
}

TSingleton* TSingleton::Instance(void)
{

return vObject;

}

void main()
{

TSingleton::GetInstance(); // this will call TSingleton::Createinstance()

TSingleton::GetInstance(); // this will call TSingleton::Instance()

// all further calls to TSingleton::GetInstance will call TSingleton::Instance() which simply returns already created object. 

}