What is Automatic Reference Counting (ARC)?
Swift version: 5.4
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.
SPONSORED Join a FREE crash course for iOS devs who want to become complete senior developers — from October 18th to 24th. Learn how to apply iOS app architecture patterns through a series of lectures and practical coding sessions.
Sponsor Hacking with Swift and reach the world's largest Swift community!
Available from iOS 8.0
Similar solutions…
- How to safely use reference types inside value types with isKnownUniquelyReferenced()
- How to fix “Ambiguous reference to member 'buildBlock()’”
- Fixing "Ambiguous reference to member when using ceil or round"
- How to display different strings based on available space using variantFittingPresentationWidth()
- How to break out of multiple loop levels using labeled statements
About the Swift Knowledge Base
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
