Re: [Pyobjc-dev] pickled Objective-C objects

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

On Sunday, Feb 23, 2003, at 22:13 Europe/Amsterdam, Just van Rossum 
wrote:

> A couple of quick thoughts.
>
[...]

> I noticed that unpickling a new style object causes cls.__new__ to be
> called. This currently does not work for ObjC classes as they insist on
> being allocated with alloc(). However, ObjC's alloc/init protocol is in
> many ways equivalent to Python's __new__/__init__ protocol, so as a
> first step towards supporting pickling, I propose to make __new__ an
> alias for alloc, and move the "TypeError: Use class methods to
> instantiate new Objective-C objects" exception to the __init__/tp_init
> method. Calling an ObjC class will then still result in that exception,
> while still properly supporting __new__.
>
Class clusters may be problematic here (in combination with pickling). 
If you create an NSArray you actually end up with a subclass of 
NSArray. This should be pickled as if it is an NSArray (Apple might 
replace the classes implementing NSArray by a completely different set 
of classes).

BTW. I just tried to pickle some Cocoa objects using protocol version 
2, and that didn't crash. It also didn't work correctly (of course): 
the Objective-C state isn't saved.

Ronald