On Jun 2, 2008, at 10:01 AM, Jens Alfke wrote:
On 2 Jun '08, at 9:12 AM, Todd Ransom wrote:
It seems that what I need is a non-retaining array. I googled
around a bit and was surprised that I could not find an existing
implementation. It looks like I can create one by subclassing
NSMutableArray, overriding the primitive methods, and using a
CFArray as the backing store with NULL callbacks to avoid any kind
of retain or release when objects are added or removed.
You can also do cool things like store integers and NULL values in
CFArray/CFDictionary/CFSet with appropriate callbacks; OmniFoundation
has some predefined callbacks that can be useful examples.
It's even easier than that, thanks to CF/NS bridging. You can just
use the CFArray API to create an array with no-op retain/release
callbacks, and then cast the CFArrayRef to NSArray* and use it as an
NSArray.
Jens alludes to using NULL retain/release, and that's a subtlety that
you might want to watch out for. If you want NSArray semantics for
things like indexOfObject:, you should write a callback function for
equality that uses isEqual:. If you pass NULL for the callbacks,
you'll get pointer equality.
--
adam
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