Automatic Reference Counting was introduced at the 2011 WWDC, in Session 323. If you want to see the original presentation, feel free to visit https://developer.apple.com/videos/play/wwdc2011/323/.
ARC is made possible by Clang and LLVM. LLVM and Clang are two technologies that enable compiling C, C++, and Objective-C code. LLVM is also used alongside the Swift compiler. With ARC, a Clang feature, developers don't have to write the tedious retain and release calls. There are multiple benefits to letting the compiler handle it, as follows:
- Memory management is difficult
- The compiler is often more correct than you are
- There are fewer lines of code to write
- It has the same performance as manual reference counting
With Swift being a modern language and the successor of Objective-C, you've never had to call retain. Swift programs leverage ARC, in order to simplify memory management. In Swift, there are multiple memory management concepts to master, and we'll cover them in this section.