A naive? attempt to create a Singleton in Swift

Singleton.swift

class FileManager {
    struct StaticInstance {
        static var instance = FileManager()
    }
    
    class var defaultManager : FileManager {
        return StaticInstance.instance
    }
}

var mgr1 = FileManager.defaultManager
var mgr2 = FileManager.defaultManager

let mustBeTrue = mgr1 === mgr2