16. Blocks
Blocks provide a way to package up some executable code and a context (various variables) as a single entity so they can be handed off for execution at a later time or on a different thread. In other languages, blocks or similar constructs are sometimes called closures or anonymous functions. Blocks are an Apple-supplied extension to C, Objective-C2.0, and C++. Apple has submitted blocks to the C standards working group as a proposed extension to C. At the time of this writing, blocks are only available on Mac OS X Snow Leopard (v 10.6 and on iOS 4). They are not available on earlier versions of Mac OS X or iPhone iOS.
Note
You can use blocks on iPhone OS 3.x and on Mac OS X Leopard (v 10.5) if you install Plausible Blocks (PLBlocks). ...
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