Hi all,
On a number of occasions I've found myself in a situation where I have
a data structure (often a complex one) that is implemented in C, but
for which I want an ObjC wrapper. As an example, let's consider a
tree of nodes.
Now, obviously it would be good to provide NSEnumerator subclasses to
iterate over the data structure. But -nextObject returns an ObjC
object, so that means writing a node wrapper class too.
Unfortunately if you do that naïvely, iterating over the data
structure will create the same number of temporary objects as the
structure has nodes.
When running without GC, there is a simple "fix" for this, which is to
re-use the existing object unless it has been -retained by something
else. i.e. only create objects if someone is storing references to
them. This way, only a single wrapper object is needed in 99.9% of
cases. Obviously this is not perfect; for instance, if you wanted to
iterate and remember one of the objects for use in a subsequent
iteration, you must retain the reference (even if you immediately
autorelease it), to stop the enumerator from re-using the object. But
it works well enough.
Under GC, these kinds of tricks are no longer possible because there
is no -retain call any more, so no way to tell if it is safe to re-
initialise and return the same wrapper object.
Aside from re-implementing the data structure itself in ObjC and
making all of its nodes objects, which might not be possible in some
cases, has anyone thought of an efficient solution to this problem
when running under GC?
(I should say that I'm not actively using GC myself in any production
code. I'm just curious to know if anyone has solved this for the GC
case.)
Kind regards,
Alastair.
--
http://alastairs-place.net
_______________________________________________
Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com
This email sent to [EMAIL PROTECTED]
