Singleton in Swift

singleton.swift

import UIKit

final class Singleton {
    static let sharedInstance = Singleton()
    private init() { }

    var value = ""
}

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let a = Singleton.sharedInstance
        a.value = "a"
        
        let b = Singleton.sharedInstance
        b.value = "b"
        
        print(a.value) // b
        print(b.value) // b
    }
}