#include <iostream>
#include <thread>
#include <mutex>
using namespace std;

mutex m;

class SingletonClass
{
    private:
        SingletonClass() { }
        SingletonClass(const SingletonClass& ) = delete ;
        SingletonClass(const SingletonClass&& )= delete ;
        //SingletonClass& operator= (const SingletonClass&) = delete ;
        //SingletonClass& operator= (const SingletonClass&&) = delete ;

    public:
        ~SingletonClass() ;
        //static SingletonClass * singletonObject;
        static unique_ptr<SingletonClass> singletonObject ;
        static SingletonClass* getInstance();
        void testObj()
        {
            cout << "Hello I am singleton :  " << this << endl;
        }
        friend std::unique_ptr<SingletonClass> std::make_unique<SingletonClass>();


};

unique_ptr<SingletonClass>SingletonClass::singletonObject = nullptr;


SingletonClass * SingletonClass::getInstance()
{
    lock_guard<mutex> lock(m);
    if(!singletonObject)
    {
        singletonObject = make_unique<SingletonClass>();
    }
    return singletonObject.get();
}

int  main()
{
    SingletonClass * s = SingletonClass::getInstance();
    s -> testObj();

    SingletonClass * s1 = SingletonClass::getInstance();
    s1 -> testObj();

    SingletonClass * s2 = SingletonClass::getInstance();
    s2 -> testObj();

    SingletonClass * s3 = SingletonClass::getInstance();
    s3 -> testObj();
    return 0;
}