Re: [Pyobjc-dev] posing

[Ronald O. <ous...@ci...>]

On Sunday, Jan 19, 2003, at 21:33 Europe/Amsterdam, bb...@ma... wrote:

> (Thinking out loud)
>
> Scratch that.    I see what is going on.
>
> The pyobj_ivar contains a reference to the Python instance that 
> effectively provides the Python side of the implementation of the 
> current class;  not just a binding to the class, but also to the 
> instance on the python side.

I thought you found a clever way around this. Sorry about not 
mentioning this before. You could of course store the reference to the 
python instance in an NSHashTable, but that would probably have a 
negative impact on performance.

>
> OK.
>
> That makes life a bit more difficult, but I *really* want posing to 
> work and, afaict, that instance variable is the only thing that is 
> holding this back.
>
> But this also raises a question regarding the eventual implementation 
> of categories.  Sort of.   With Categories, one needs to add Python 
> implemented methods to an already existing class.
>
> Rephrase:  Categories and posing are effectively the same problem:   
> they both imply that a class will preexist and that the category (or 
> posing class) will not add any instance variables within its 
> declaration.

With libFFI it is possible to implement categories without adding an 
instance variable. One of the features of libFFI is the possibility to 
define closures that look like normal functions. A method in a 
categorie can be implemented using a closure that contains a reference 
to the python function implementing the method.

The same trick could be used for mixed classes: 
__pyobjc_pythonImplementation__ would also be a closure.

Ronald