On Sun, 29 Jun 2014 01:07:11 -0400, Kapps <[email protected]> wrote:
On Friday, 27 June 2014 at 21:23:52 UTC, Mark Isaacson wrote:
If I have a variable whose static type is an interface and I call
typeid on it, I get the interface back, not the dynamic type.
This seems like confusing behavior. Is this the intended result?
I recognize that one needs some amount of state to perform the
dynamic type lookup, and so it is on that thought that a reason
for this might be based.
Interfaces are not necessarily Objects (particularly with the case of
IUnkown or extern(C++)), and are handled somewhat differently from
objects.
As I've said many times, instances of D interfaces are necessarily
Objects. Any D class that implements a D interface is a D object, and
should implicitly cast to Object.
When you cast to Object, you're actually subtracting a few bytes from
the pointer to get back to the Object, so technically the variable
refers not to Object but to the interface. It is a bit odd (along with
some of the other side-effects), but it does make some sense since
you're referring to the interface and not to an Object.
Correct. It would be a trivial extra-step of subtraction to get the
TypeInfo of the class itself.
That being said, I'm not 100% sure whether this is the intended
behaviour when you actually do point to a class derived from Object.
It is the intended behavior. And I think your reasoning of the IUnknown
problem is the intended reasoning. And I think it's wrong :)
-Steve
