Extern function inside a class?
Daniel Keep
daniel.keep.lists at gmail.com
Sat Jun 23 22:04:31 PDT 2007
Gilles G. wrote:
> Hello,
> I am writing a DLL using D. Iwould like to group the functions that I export together in a class which would also keep the data.
> For example:
> class DllManager
> {
> this(){}
> ~this(){}
> invariant int dllVersion 1;
> MyObject[] objectList;
> extern(Windows) int GetDllVersion() { return dllVersion;}
> extern(Windows) int NewObject()
> {
> objectList.length = objectList.length+1;
> return objectList.length;
> }
> }
> But I wonder if this is possible, because there is no instance of the class DllManager available. What happens when the function NewObject is called by the main program?
>
> I guess the good way to do this is:
> class DllManager
> {
> this(){}
> ~this(){}
> invariant int dllVersion 1;
> MyObject[] objectList;
> int GetDllVersion() { return dllVersion;}
> int NewObject()
> {
> objectList.length = objectList.length+1;
> return objectList.length;
> }
> }
> DllManager manager;
> extern(Windows) int GetDllVersion() {return manager.getDllVersion(); }
> extern(Windows) int NewObject() {return manager.NewObject();}
>
> But it looks like I am forced to write all the external calls twice...
>
> Anybody for a "cleaner" solution?
> Thanks!
The problem with your second example is that it doesn't work, either.
"DllManager manager;" does *NOT* create an instance of DllManager: it
simply defines a variable that can point to one.
The question is: why do you want to use a class? I mean, classes aren't
required in D, and you can't export classes through DLLs, so using a
class doesn't gain you anything.
Judging from how you're using it, you could easily just not use a class
at all, and use globals. Then you wouldn't need to wrap all the calls.
It's not like using globals will cause the world to explode, or anything :)
-- Daniel
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