What is a singleton?
Swift version: 5.4
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.
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Available from iOS 8.0 – learn more in my book Swift Design Patterns
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This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
