Denis Koroskin Wrote: > On Tue, 18 Nov 2008 17:17:36 +0300, Michel Fortin > <[EMAIL PROTECTED]> wrote: > > > On 2008-11-17 13:56:55 -0500, Harry Vennik <[EMAIL PROTECTED]> said: > > > >> Hi, > >> One of the things D claims is that it eliminates the need for IDL. And > >> yeah, it does a lot in that direction, but I found something that's > >> missing while trying to actually implement some sense of RPC... > >> To get a good view of an interface that can be used to construct the > >> necessary stub code, you need to have a typed vtable. And D almost > >> provides it... You can get the untyped vtable, you can get a typed list > >> of virtual function overloads by name, and you can get the names of all > >> interface members... So you can get all what's needed, except that > >> there is no way to know the vtable index of a member function!!! > >> My proposal to fix this is to allow an expression like: > >> __traits(getVirtualFunctions, T) // no second argument! > >> where T is an interface or class type (or an expression of such a > >> type). Such an expression should then return all virtual member > >> functions in vtable order, thus making it possible to relate the > >> function itself to its vtable index. > > > > Personally, I had to work around the same problem in the D/Objective-C > > bridge and thus I could probably simplify a few things by having this, > > except that what I need in my case is always the vtable index of a > > particular function. I guess it could be implemented from the above > > __traits syntax, but I'd wish for a simpler solution to my problem, such > > as: > > > > __traits(getVTableIndex, T.foo); > > > > along with a way to check if a function is virtual, possibly by checking > > they're not final: > > > > static if (is(T.foo == final)) ...; > > > > This way I could build a pointer template-struct to a virtual member > > function (without knowing the target object in advance as with > > delegates). > > > > > > What if class T has multiple foo() overloads, half of which are virtual > and half are not?
Michel's proposed solution won't work then... I have also run into the question 'how to select a particular overload' and realised that probably that is the reason why the __traits are designed as a two-level approach: first get the member names, then get the virtual overloads of each... The possibility that someone might also want all virtual methods in vtable order seems to be just forgotten. By the way, I think that my proposal will also solve Michel's problem, as it is very similar to mine. The language bindings can also be generated from a tuple of functions. The index in the tuple is the vtable index... Although it might be off by one, because D uses index 0 of the vtable to store a reference to the ClassInfo (I never understood why... but it is a fact...). Please note that for my solution to work, it is also required that the order of functions in the vtable is defined, because recompilation of the same source must result in the same vtable order again. (I'd define the order like: in source order, and 'base' class/interface before 'derived' class/interface.) I don't know if this is actually defined now...
