懒汉模式

class Singleton{
public:
    static Singleton& getInstance(){
        if(m_pIntance == nullptr){
            m_mutex.lock();                        // 互斥锁，保证多线程中也是单例的。
            if(m_pIntance == nullptr){
                m_pIntance = new Singleton();
            }
            m_mutex.unlock();
        }
        return m_pInstance;
    }
    void fuck(){
        cout << "fuck something" << endl;
    }
private:
    Singleton *m_pIntance;
    std::mutex m_mutex;
    Singleton() = delete;                                        //阻止外部构造
    Singleton(Singleton const &singleton) = delete;                //阻止拷贝构造
    Singleton& operator=(Singleton const &singleton) = delete;    //阻止拷贝赋值
};
main()
{
    Singleton::getInstance().fuck();
}

饿汉模式

class Singleton{
public:
    static Singleton& getInstance(){
        static Singleton instance;        //在程序启动时就加载，线程安全。
        return instance;
    }
    void fuck(){
        cout << "fuck something" << endl;
    }
private:
    Singleton() = delete;                                        //阻止外部构造
    Singleton(Singleton const &singleton) = delete;                //阻止拷贝构造
    Singleton& operator=(Singleton const &singleton) = delete;    //阻止拷贝赋值
};
main()
{
    Singleton::getInstance().fuck();
}