c++单例模式

class Sigleton
{
private:
    Sigleton() { std::cout << "Sigleton constructor" << std::endl; };
    ~Sigleton();
    Sigleton(const Sigleton &other) = delete;
    Sigleton &operator=(const Sigleton &) = delete;

public:
    static Sigleton *Instance()
    {
        if (nullptr == instance_)
        {
            instance_ = new Sigleton();
        }
        return instance_;
    };

    static void Test()
    {
        Sigleton::Instance();
        Sigleton::Instance();
    }

private:
    // declare staic member instance_
    static Sigleton *instance_;
};

// define staic member instance_
Sigleton *Sigleton::instance_ = nullptr;

class Sigleton
{
private:
    Sigleton() { std::cout << "Sigleton constructor2" << std::endl; };
    ~Sigleton();
    Sigleton(const Sigleton &other) = delete;
    Sigleton &operator=(const Sigleton &) = delete;

public:
    static Sigleton *Instance()
    {
        return instance_;
    };

    static void Test()
    {
        Sigleton::Instance();
        Sigleton::Instance();
    }

private:
    // declare staic member instance_
    static Sigleton *instance_;
};

// define staic member instance_
Sigleton *Sigleton::instance_ = new Sigleton();