[vtk-developers] Unique PIMPL class names

[Bill Hoffman]

Nested classes are not supported by all compilers.
Specifically, you can not forward declare a nested class,
and put the implementation in a .cxx file which is what we need
for "Pimpl".   Due to some dashboard errors, we recently had
to change some code like this:

---vtkFoo.h----
class vtkFoo
{
  private:
   class vtkBar;  // forward declare nested class
   vtkBar* Bar;
};

----vtkFoo.cxx-----
class vtkFoo::vtkBar : public vtkstd::vector<int>  // error on some compilers
{
};

The only portable fix, was to change it to this:
---vtkFoo.h----
class vtkFooBar;
class vtkFoo
{
private:
 vtkFooBar* Bar;
};

---vtkFoo.cxx---
class vtkFooBar : public vtkstd::vector<int>
{
};



>Why not declare them as member classes of vtkFoo instead of
>making really long classnames?
>class vtkFoo
>{
>  private:
>    class Bar {
>    }
>};
>
>Inside member functions of vtkFoo, you don't need to type
>vtkFooBar, just Bar. If declared as private members (as
>above) no one can use this class externally. If declared
>as public members, then others can reference the class
>name as vtkFoo::Bar.
>
>                David