[vtkusers] Cross Delegation with vtkSQLDatabase

[David Thompson]

> I'm wanting to do something similar to this. I'm guessing part of the
> reason why I can't is because vtkSQLiteDatabase, vtkMySQLDatabase etc
> etc don't virtually inherit vtkSQLDatabase?

Yes, that's correct; since pretty much everything in VTK inherits  
vtkObject, inheriting multiple subclasses of vtkObject leaves a bunch  
of methods the compiler cannot unambiguously resolve. I suspect that  
virtual inheritance was not supported by all the compilers that VTK  
supports (the list changed over the last year so that may no longer be  
true), and at least some compilers produce code which adds overhead  
otherwise avoided without virtual inheritance. At least for now,  
you're probably stuck owning an instance of vtkSQLDatabase instead of  
inheriting it.

	David

> ----------
> #include "vtkSQLDatabase.h"
> #include "vtkSQLiteDatabase.h"
> #include "vtkMySQLDatabase.h"
>
> class mySQLDatabase : public virtual vtkSQLDatabase
> {
>        bool foo()
>        {
>                //do foo
>                return true;
>        }
> };
>
> class mySQLiteDatabase : public vtkSQLiteDatabase, public  
> mySQLDatabase
> {
> };
>
> class myMySQLDatabase : public vtkMySQLDatabase, public mySQLDatabase
> {
> };
>
> int main()
> {
>        mySQLiteDatabase database();
>        database.foo();
> }
> ----------
>
> Is this something VTK should try to accommodate? Or is there already a
> way of doing this?
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtkusers
>