RE: [GD-General] Multiple Inheritance and RTTI

[Gareth L. <GL...@cl...>]

> Out of curiosity, can someone post a real example of using the
> QueryInterface pattern (in performance-critical code)?

QueryInterface is fairly quick. A lot depends on the number of interfaces
you are implementing per object.

But most things use macros like

(note, this is psuedo code.)

START_INTERFACELIST
	ADD_INTERFACE(IID_IRender)
	ADD_INTERFACE(IID_IFoo)
END_INTERFACELIST

which becomes somethinglike

bool QueryInterface(GUID iid, void** ppObject)
{
	if (iid == IID_IRender)
	{
		(*ppObject) = reinterpret_cast<void*>(this);
		return true;
	}
	if (iid == IID_IFoo)
	{
		(*ppObject) = reinterpret_cast<void*>(this);
		return true;
	}
	(*ppObject)=0;
	return false;
}

GUIDs can be anything. You could go the extreme "time+network card" which is
overkill. FourCCs work very well as well. As long as you make sure not to
clash. Depends on the size of the team I guess.

If you have a lot of interfaces per concrete class you might need a diff
solution.