C++ 单例设计模式

#include <iostream>

using namespace std;

// 单例模式 --- 懒汉式
class Singleton
{
private:
    Singleton()
    {

    }
public:
    static Singleton* GetInstance()
    {
        if (m_instance == nullptr)
            m_instance = new Singleton;

        handle_count++;
        return m_instance;
    }

    static void Release()
    {
        if (handle_count > 0)
            handle_count--;

        if (m_instance != nullptr && handle_count == 0)
		{
			delete m_instance;
			m_instance = nullptr;
		}
    }

private:
    static int handle_count;       // 引用计数
    static Singleton* m_instance;
};

Singleton* Singleton::m_instance = nullptr;
int Singleton::handle_count = 0;

int main()
{
    // Singleton s1;
    // Singleton s2;

    Singleton* ps = Singleton::GetInstance();
    Singleton* ps1 = Singleton::GetInstance();
    Singleton* ps2 = Singleton::GetInstance();
    Singleton* ps3 = Singleton::GetInstance();

    cout << ps << endl;
    cout << ps1 << endl;
    cout << ps2 << endl;
    cout << ps3 << endl;

    Singleton::Release();
    Singleton::Release();


    return 0;
}