Recent versions of iOS and the Apple LLVM 2.1 compiler use an improved version of
libobjc, the core library that powers Objective-C features like classes and method calls. This "modern runtime" library enables a lot of new, cool flexibility in creating Objective-C classes. One of my favorite new features is Instance Variables in the Implementation File, which allows you to move your private instance variables out of your
.hfiles. iOS developer Tips shows you how.