Pointer to class?

Really basic question:
I'm just wondering how you use a class in an external function, here's the relevant code I've tried, but which obviously, doesn't work:

Code:

---

Lf::Lf(int x, int y, Grid *mygrid)
{
  mygrid.addGridEntity(x, y, 'o');
}

int main()
{
  Grid mygrid;
  Lf mylf(3, 3, &mygrid);
  mygrid.printGrid();
}

---

you can either use pointers:

Code:

---

Lf::Lf(int x, int y, Grid* mygrid)
{
  mygrid->addGridEntity(x, y, 'o'); // use arrow not dot when dealing with a pointer
}

int main()
{
  Grid mygrid;
  Lf mylf(3, 3, &mygrid);
  mygrid.printGrid();
}

---

or references

Code:

---

Lf::Lf(int x, int y, Grid& mygrid)
{
  mygrid.addGridEntity(x, y, 'o'); // use dot with a reference
}

int main()
{
  Grid mygrid;
  Lf mylf(3, 3, mygrid); // address is taken implicitly with reference initialization
  mygrid.printGrid();
}

---

Thanks. I always knew you were smarter than me.