Swift version: 5.6
Singletons are objects that should only ever be created once, then shared everywhere they need to be used. They are common on Apple’s platforms: FileManager
, UserDefaults
, UIApplication
, and UIAccelerometer
are all mostly used through their singleton implementations.
The basic implementation of a Swift singleton looks like this:
class Settings {
static let shared = Settings()
var username: String?
private init() { }
}
Adding a private
initializer is important, because it stops other parts of our code from trying to create a Settings
class instance. However, the class creates its own instance of itself as a static variable, which means the only instance of the Settings
class is the one it created: Settings.shared
.
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 – learn more in my book Swift Design Patterns
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
Link copied to your pasteboard.