Re: gnustep/base modifications for OSX

[Richard Frith-Macdonald]

On Tuesday, January 28, 2003, at 09:46  pm, David Ayers wrote:

> 1. Do we send copy/copyWithZone: and have more or less undefined 
> results on level down? I would be against this, but convince me if you 
> think it's correct.
>
> 2. Do we call a potential shallowCopy/shallowCopyWithZone: which could 
> be implemented in the abstract collection classes as 
> AUTORELEASE([[[self class] alloc]initWithCollection: self] and 
> NSObject might implement it by calling copyWithZone:  allowing only 
> one level of "deepness".
>
> 3. Or should deepCopy also propagate deepCopy/deepCopyWithZone:? and 
> NSObject might implement it by calling copyWithZone: also.
>
> I guess, in the case of a plist structure, if I deepCopy the root 
> object, I would expect a full deepCopy of all the contents.  So I'm 
> leaning towards 3.  2. can trivially implemented by any code that 
> needs it.

I think a basic copy would be a shallow copy.

For a truly deep copy, you would just use NSArchiver/NSUnarchiver to
duplicate the entire data structure.

Anything else, you probably have to implement yourself on a class by 
class basis.

> PS: If I remember correctly, a lot of gdl2's usage of copy/mutablCopy 
> on collection classes was intended for conversions between mutable and 
> non-mutable counterparts.  I'm wondering whether we could/should 
> introduce a shallowMutableCopyWithZone: and define that 
> shallowCopyWithZone: always returns immutable counterparts.  I'm not 
> clear on whether a deepMutableCopyWithZone: would also be needed to 
> have a complete defined implementation or whether we're going over 
> board.

I think the standard copy (shallow) does the job of making a collection 
immutable ... but it doesn't make its contents immutable.
There is nothing I can think of in the API which will make an entire 
data structure immutable (except for property lists).