Opting into and out of ARC

In the newest Xcode, all new projects are created ARC compliant. Old-style projects imported into the new Xcode do not transition to ARC until you migrate your code. Migration is offered in Edit > Convert > Convert to Objective C Automatic Reference Counting. Migration helps you move from memory managed code (manual retain/release, or MRR) to ARC.

Thoroughly back up your projects first. No matter how much Xcode offers to help you with that, it’s best to protect yourself. Create your own revision point that you can move back to outside of Xcode auspices.

Migrating to ARC

Xcode migration assists you through the process of changing both settings and code. Your project updates to use the LLVM 3.0 compiler and is prescanned for lexical issues. Lexical issues will include any in-code autorelease pools as well as any other potential conflicts. The migration tool tags these, allowing you to manually alter items as needed before it begins the in-code conversion.