Blocks in Objective-C
Apple is adding blocks (a.k.a. closures) to Objective-C (via Ian Baird):
From a technical perspective, blocks fit into C in a couple places: 1) a new declaration type (the caret) which work very much like a magic kind of pointer that can only point to function types. 2) block literals, which capture the computation 3) a new storage class __block 4) a really tiny runtime library.
The new storage class comes into play when you want to get mutable access to variables on the stack. Basically you can mark an otherwise- auto variable with __block…
Update (2008-08-30): Jens Alfke comments.
[...] and a variable number of arguments, and it performs the selector on each object in the array. Blocks are much nicer, of course, but they’re not available yet in Objective-C. Higher order [...]