Re: [Pyobjc-dev] conversion of tuples to structs

[Just v. R. <ju...@le...>]

Tobias Sargeant wrote:

> Looking at the code in objc_support.m, it's pretty obvious that
> structs (and arrays) can currently only be built from tuples. Is
> there any reason why anything that acts as a sequence won't do?

Not really. In the Carbon(-ish) wrappers that come with MacPython we've
usually made sure this is possible. For example the Carbon.CG module
accepts any length-6 sequence where it expects an affine transform. Very
useful (especially since I have a Transform class that also behaves as a
length-6 sequence ;-). The same goes voor points and rects.

> I appreciate that the symmetry of the pythonifying/depythonifying is
> neat, but it would be extremely useful (for example) to be able to
> pass Numeric arrays representing points to objc functions without the
> overhead (both in terms of execution speed and in terms of typing) of
> converting them to tuples.
> 
> If there's no reason (technical or otherwise) why this shouldn't be
> the case, I'm happy to make the change and submit a patch.

I've been thinking the same thing every now and then. I don't know how
easy it would be to fix. If those structs were unpacked with
PyArg_ParseTuple (and I think they aren't), the fix would be easy: just
use PyArg_Parse instead and add parenthesis to the format strings, eg.
"ff" would have to become "(ff)". But I have no idea where the struct
conversions live in the PyObjC code base... Ronald?

Just