Swift version: 5.6
Unowned variables are similar to weak variables in that they provide a way to reference data without having ownership. However, weak variables can become
nil – they are effectively optional. In comparison, unowned variables must never be set to nil once they have been initialized, which means you don't need to worry about unwrapping optionals.
The most common place you'll see unowned variables is with closures that declare
[unowned self] – this means "I want to reference
self inside this closure but I don't want to own it." Why
unowned rather than
weak? Both would work, but let's face it: if
self is nil inside a closure, something has gone wrong!
SAVE 50% To celebrate Black Friday, 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 7.0
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
Link copied to your pasteboard.