单实例模式

最新推荐文章于 2024-09-12 15:38:53 发布

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// copy from reset
#pragma once
#include <mutex>

template <typename T>
class Singleton
{
public:
    static T* Instance()
    {
        std::call_once(initFlag, create);
        return instance;
    }

protected:
    Singleton() = default;
    ~Singleton() = default;

private:
    Singleton(const Singleton&) = delete;
    Singleton& operator=(const Singleton&) = delete;
    Singleton(Singleton&&) = delete;
    Singleton& operator=(Singleton&&) = delete;

private:
    static void create()
    {
        instance = new T;
        std::atexit(&Singleton<T>::destroy);
    }

    static void destroy()
    {
        delete instance;
    }

    static std::once_flag initFlag;
    static T* instance;
};

template <typename T> std::once_flag Singleton<T>::initFlag;
template <typename T> T* Singleton<T>::instance = nullptr;