How to put Gtk:Grid in Gtk:Window with gtkmm
===

How can I put Gtk:Grid in Gtk:Window using gtkmm. It says "*no known conversion for argument 1 from «Gtk::Grid()» to «Gtk::Widget&»*" when I'm trying to call `main_win.add(grid);`
This works but it's too ugly:

	...
	int main (int argc, char *argv[])
	{
	
	Main kit(argc, argv);
	
	Label label1("Hello1",0,0.5);
	Label label2("Hello2",0,0.5);
	
	Grid grid;
	
	(*((Container*)&grid)).add(label1);
	(*((Container*)&grid)).add(label2);
	
	Window main_win(Gtk::WINDOW_TOPLEVEL);
	main_win.add(*((Widget*)&grid));
	
	main_win.show_all();

	kit.run(main_win);
	
	return 0;
	}