source/Tactical/LogicalBodyTypes/Singleton.h

#pragma once
#ifndef _LBT_SINGLETON__H_
#define _LBT_SINGLETON__H_

#include <cassert>

/*
Not thread safe. Copied from the codeproject (Author: Lai Shiaw San Kent)
*/

template<typename T> class ISingleton {
public : 
    static T& Instance();
};

template<typename T> class Singleton : public ISingleton<T> {

public :
	static T& Instance();
    static void Destroy();

protected : 
    inline explicit Singleton() { 
        assert(Singleton::instance_ == 0); 
        Singleton::instance_ = static_cast<T*>(this); 
    }
    inline ~Singleton() { 
        Singleton::instance_ = 0; 
    }

private : 
    static T* CreateInstance();
    static void ScheduleForDestruction(void (*)());
    static void DestroyInstance(T*);

private : 
    static T* instance_;

private : 
    inline explicit Singleton(Singleton const&) {}
    inline Singleton& operator=(Singleton const&) { return *this; }
};


template<typename T> typename T& Singleton<T>::Instance() {
    if (Singleton::instance_ == 0) {
        Singleton::instance_ = CreateInstance();
        ScheduleForDestruction(Singleton::Destroy);
    }
    return *(Singleton::instance_);
}

template<typename T>
void Singleton<T>::Destroy() {
    if (Singleton::instance_ != 0) {
        DestroyInstance(Singleton::instance_);
        Singleton::instance_ = 0;
    }
}

template<typename T>
inline typename T* Singleton<T>::CreateInstance() {
    return new T();
}

template<typename T>
inline void Singleton<T>::ScheduleForDestruction(void (*pFun)()) {
    std::atexit(pFun);
}

template<typename T>
inline void Singleton<T>::DestroyInstance(T* p) {
    delete p;
}

template<typename T>
typename T* Singleton<T>::instance_ = 0;

#endif