#include <iostream>

using namespace std;

class Tick
{
private:
    static Tick instance;

    int tick;
public:
    static const Tick& GetInstance()
    {
        return instance;
    }

    static void Update()
    {
        instance.SetTick(instance.GetTick()+1); //tudom kicsit erőltetett a példa, már csak azért is, mert az Update eléri az instance private attribútumait is
    }

    Tick()
    {
        tick=0;
    }

    const int GetTick() const
    {
        return tick;
    }

    void SetTick(const int t)
    {
        if(t>tick)
        {
            tick=t;
        }
    }
};

Tick Tick::instance;

int main()
{
    const Tick& tick=Tick::GetInstance();
    cout << tick.GetTick() << endl; //0

    tick.Update();
    cout << tick.GetTick() << endl; //1

    tick.SetTick(10);   //Error 1   error C2662: 'Tick::SetTick' : cannot convert 'this' pointer from 'const Tick' to 'Tick &'
    cout << tick.GetTick() << endl; //1

    return 0;
}