Re: error MIDL2025 : syntax error : expecting { near ","
Donos <donguy76@gmail.com> wrote:
Now is a more tricky question, i guess
interface IVehicle : IUnknown
{
};
interface ICar : IVehicle
{
};
interface IHonda : ICar
{
};
interface IToyota : ICar
{
};
In this case, should i contunue to derive from both IHonda and
IToyota?
And should i keep all interfaces in COM MAP Entry?
You should derive both from IHonda and IToyota. You should use
COM_INTERFACE_ENTRY2 to list ICar in an interface map (choose either
IHonda or IToyota to disambiguate, it doesn't matter which).
Better still, you should sit and think why you feel you need such a
complicated inheritance hierarchy. While looking great in a textbook, in
most practical situations an inheritance hierarchy more than two levels
deep is a sign of bad design.
COM interfaces should not model entities - they should model sets of
behaviors. What can ICar do that IVehicle can't? Break this
functionality into a separate interface (e.g. ICarLike) derived directly
from IUnknown, and have the COM object implement both side by side.
--
With best wishes,
Igor Tandetnik
With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925