[PyKDE] static const member variables

[Phil Thompson]

On Tuesday 11 July 2006 11:15 pm, Nigel Stewart wrote:
> Hello all,
>
> I'm sure this issue has come up before, in one way or another.
>
> Our issue is to do with static const class member variables
> such as:
>
> class A
> {
> public:
>      static const A zero;
>      static const A one;
> ...
> }
>
> ...In much the same manner as Qt provides QString::null.
>
> The problem we're having is that without a concept of constness
> in Python, we have the risk of python-code changing A::zero,
> A::one or QString::null.
>
> So, we were thinking of using %AccessCode (or something similar)
> to provide copies to Python that can be changed, leaving the
> C++ static const safe from modification....
>
> class A
> {
> ...
>      static const A zero;
> %AccessCode
>      return new A(A::zero);
> %End
> ...
>
> But then, it seems likely that these copies will be leaked, so
> we seem to be stuck...
>
> Perhaps SIP could support a variable annotation that indicates
> that a copy should be passed to Python, rather than a reference,
> as an approximation to const in C++.
>
> (For a static member function we would be able to use
>   TransferBack to transfer ownership of the copy to Python)
>
> Perhaps more ideally, a const-flavored SIP wrapper object could
> omit the non-const methods - resulting in a lighter-weight and
> more general purpose solution to the problem.

Proper support for const has been on the TODO list for a long time - just 
haven't got around to it yet.

Phil