74 videos totalling 5.25 hours of training in the language and tools you'll need to program iOS and OS X. Find out more here.
Objective-C has been changing recently. There were major changes in Objective-C 2.0, but that was released in 2007, and six years can be an eternity in the software world. Since 2007, new features have been added including Automatic Reference Counting (ARC), blocks, literals, and subscripts. With the latest releases of Xcode, new tools are available in Edit/Refactor to convert your legacy code to use ARC and modern syntax. This is a change from previous guidance which suggested that adopting ARC on existing projects wasn't recommended. Now it's not only recommended but automated.
Blocks are perhaps one of the most critical changes. They are not unique to Objective-C (they're often called closures in computer science courses). They consist of functions or function references together with a referencing environment consisting of the non-local variables that are needed by the block. Blocks are sweeping through the Cocoa and Cocoa Touch frameworks often replacing callback functions. As more and more of our apps are multi-threaded and asynchronous, blocks provide an excellent non-linear way of developing code.
Put together, these recent changes mean that if you've been putting off learning Objective-C, now is the right time to jump in, and this video can help. If you learned Objective-C in the past, now is the time for a refresher to bring your knowledge up to date.