Learning Objective-C 2.0: A Hands-on Guide to Objective-C for Mac and iOS Developers, Second Edition

17. 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-C 2.0, and C++. Apple has submitted blocks to the C standards working group as a proposed extension to C. Blocks are available on Mac OS X 10.6 or later and iOS 4.0 or later.

Note

You can use blocks on iOS 2.2+ and on Mac OS X Leopard (10.5) if you install Plausible Blocks (PLBlocks). Plausible Blocks, a reverse-engineered port from Apple-released open-source Darwin OS code, provides the ...