In this case to access to properties of class you should cast it inside

Yes I would not do it this way. I would specify the order. This is for Liskov as someone pointed out. Anyone should be able to make

class MyGridLayoutManager: GridLayoutManager

and your code should still work as though it's a

GridLayoutManager

. If you look at specific classes, your code is not allowing substitution.

Thanks for your answers 🙂