Swift version: 5.6
Automatic Reference Counting (ARC) is Swift’s system of tracking memory you’re using. When you create an object from a class, Swift remembers that instance is being referenced precisely once. If you then point another variable at that object, Swift will increment the reference count to 2, because two variables are pointing at the same object. If you now destroy the first variable (perhaps it was inside a function and that function ended), Swift takes the reference count back down to 1.
All this matters because as long as the reference count is greater than 1 the object stays alive. But when the final variable referencing that object goes away, Swift will take the reference count down to zero. As no existing variables point at the object, its RAM can be released. So, ARC is a way of tracking an object’s lifetime efficiently, and for the most part you don’t even notice it happens – Swift does all the work for you.
SAVE 50% To celebrate WWDC23, all our books and bundles are half price, so you can take your Swift knowledge further without spending big! Get the Swift Power Pack to build your iOS career faster, get the Swift Platform Pack to builds apps for macOS, watchOS, and beyond, or get the Swift Plus Pack to learn advanced design patterns, testing skills, and more.
Available from iOS 8.0
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
Link copied to your pasteboard.