Written by Paul Hudson @twostraws
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:
struct Settings {
static let shared = Settings()
var username: String?
private init() { }
}Adding an initializer to the Settings struct automatically disables the default memberwise initializer, and it’s marked private so that it also can’t be called from outside the class. However, the struct creates an instance of itself as a static variable, which means the only instance of the Settings struct is the one it created: Settings.shared.
Available from iOS 8.0 – learn more in my book Swift Design Patterns
Did this solution work for you? Please pass it on!
Other people are reading…
About the Swift Knowledge Base
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
Learn Swift faster!
Take your Swift learning to the next level: buy the Hacking with Swift e-book and get bonus material to help you learn faster!