Singleton.hpp

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// Copyright 2022-2024 Jan Niklas Hasse <jhasse@bixense.com>
// For conditions of distribution and use, see copyright notice in LICENSE.txt
#pragma once
 
#include "window.hpp"
 
namespace jngl {
 
template <class T> class Singleton {
public:
    ~Singleton() = default;
    Singleton(const Singleton&) = delete;
    Singleton& operator=(const Singleton&) = delete;
    Singleton(Singleton&&) = delete;
    Singleton& operator=(Singleton&&) = delete;
 
    static T& handle() {
        if (!instance) {
            instance = new T;
            atExit(&Singleton::destroy);
        }
        return *instance;
    }
 
    [[nodiscard]] static T* handleIfAlive() noexcept {
        return instance;
    }
 
    static void destroy() noexcept {
        delete instance;
        instance = nullptr;
    }
 
protected:
    Singleton() = default;
 
private:
    static T* instance;
};
 
template <class T> T* Singleton<T>::instance = nullptr;
 
} // namespace jngl