Re: [Pyobjc-dev] Headache over hacking an XML editor

[<bb...@ma...>]

On Tuesday, Jan 14, 2003, at 13:57 US/Eastern, Just van Rossum wrote:
> Ugh, this is depressing :-(. (So you _can_ find out the return type of 
> a
> method at runtime but not whether it returns a new or a borrowed
> reference. Great.)

Correct.   There is no concept of 'new vs. borrowed' at anything but 
the object level.

This isn't a problem from the Objective-C side of the fence -- it is 
only a problem in that Python and ObjC take different approaches to 
solving the memory management problem.   I like Python's a lot better, 
but I have to live with ObjC's because I'm leveraging ObjC frameworks-- 
even when writing PyObJC code.

> Here's a quick idea to work around the most common (I think) 
> irritation:
> instead of raising an exception when calling a (subclass of) NSObject
> ("TypeError: Use class methods to instantiate new Objective-C objects")
> have objc-object.m::object_new() do this:
>
>         self = cls.alloc()
>         self.release()  # ownership transferred to the Python wrapper
>         return self

This code is lacking the call to the -init method -- problematic.

What about arguments to the constructor?  We can handle the no argument 
case transparently, but what about-- say-- NSView's -initWithFrame: 
designated initializer?

Also, keep in mind that -init* methods return an object reference for a 
reason;  a number of intializers return a different instance than the 
one that was called for a number of [valid] reasons.

> This doesn't touch the alloc() semantics, yet provides a much more
> Pythonic way to create instances. Heck, this will even call __init__()
> for you! ;-)

But __init__() is not generally the designated intiailizer for ObjC 
classes-- even Python implemented subclasses of ObjC classes.

When subclassing ObjC from Python, it makes more sense to follow the 
ObjC semantics than the Python semantics -- at least, it does to me.

> What I still don't understand is how pyobjc manages the refcount of
> Python objects passed to objc: the Python object can't have a reference
> to it, so when will the wrapper be released? Is it an autorelease
> object?

Ronald can better answer this question.

b.bum