单例模式

懒汉模式

class singleton{
private:
    singleton(){};
    static singleton* m_instance;
    singleton(const singleton&)=delete;
    singleton& operator=(singleton&)=delete;
public:
    static singleton* getInstance();
    ~singleton(){};
};
singleton* singleton::m_instance = nullptr;

singleton* singleton::getInstance(){
    if (m_instance == nullptr) {
        lock;
        if (m_instance == nullptr) {
            m_instance = new singleton();
        }
        unlock;
    }
    return m_instance;
}