GxSingleton.h

//===========================================================================
//===========================================================================
#pragma once
 
GX_CORE_NAMESPACE_BEGIN()
 
//===========================================================================
//===========================================================================
template <typename T>
class SingletonBase
{
    //-------------------------------------------------------------
    //-------------------------------------------------------------
public:
    SingletonBase(void)
    {
        GX_ASSERT(_pInstance == nullptr, "already exist");
        size_t offset = (size_t)(T*)1 - (size_t)(SingletonBase<T>*)(T*)1;
        _pInstance = (T*)((size_t)this + offset);
    }
 
    ~SingletonBase(void)
    {
        GX_ASSERT(_pInstance != nullptr, "already deleted");
        _pInstance = nullptr;
    }
 
private:
    // コピーコンストラクタ（使用禁止）
    SingletonBase(const SingletonBase& singletonBase);
    // 代入演算子（使用禁止）
    const SingletonBase& operator = (const SingletonBase& singletonBase);
 
    //-------------------------------------------------------------
    //-------------------------------------------------------------
public:
    GX_FORCE_INLINE static T& getSingleton(void)
    {
        GX_ASSERT(_pInstance, "has not initialized");
        return *_pInstance;
    }
    constexpr static T* getSingletonPointer(void){ return _pInstance; }
 
    //-------------------------------------------------------------
    //-------------------------------------------------------------
private:
    static T* _pInstance;   
 
};
 
template <typename T>
T* SingletonBase<T>::_pInstance = nullptr;
 
GX_CORE_NAMESPACE_END()