C++设计模式之单例模式

#include <iostream>
using namespace std;

class Singleton {
private:
    static pthread_mutex_t mtx;
    static Singleton *instance;
    Singleton() {}
    ~Singleton() {}
public:
    static Singleton* getInstance ()
    {
        if(instace == nullptr)
        {
            pthread_mutex_lock(mtx);
            if(instance == nullptr)
            {
                intstance == new Singleton();
            }
            pthread_mutex_lock(mtx);
        }
        return instance;
    }
};
pthread_mutex_t Singleton::mtx == PTHREAD_MUTEX_INITIALIZER;
Singleton* Singleton::instance =  nullptr;

int main()
{
    Singleton* test = Singleton::getInstance();
}

饿汉：

class singleton
{
protected:
    singleton()
    {}
private:
    static singleton* p;
public:
    static singleton* initance();
};
singleton* singleton::p = new singleton;
singleton* singleton::initance()
{
    return p;
}

 参考资料：

C++的单例模式与线程安全单例模式（懒汉/饿汉）