Can this Singleton object use type stored properties instead in Swift2?

Question

I read that creating a struct or global constant was required to implement the singleton pattern in Swift as "Swift doesn't support type stored properties"

final class BackupServer {

    let name:String;
    private var data = [DataItem]();

    private init(name:String) {
        self.name = name;
        globalLogger.log("Created new server \(name)");
    }

    func backup(item:DataItem) {
        data.append(item);
        globalLogger.log("\(name) backed up item of type \(item.type.rawValue)");
    }

    func getData() -> [DataItem]{
        return data;
    }

    class var server:BackupServer {
        struct SingletonWrapper {
            static let singleton = BackupServer(name:"MainServer");
        }

        return SingletonWrapper.singleton;
    }
}

Is this still true in Swift2? I am learning how to implement the Singleton pattern in Swift for my own interest and don't need to be told it is an anti-pattern. The docs seem to say that stored type properties are possible

Answer 1

The best way I've seen to create a singleton in Swift is the following:

class SingletonClass {
    static let sharedInstance = SingletonClass()
    private init() {} //This prevents others from using the default '()' initializer for this class.
}

You can read the full explanation here: http://krakendev.io/blog/the-right-way-to-write-a-singleton

Answer 2

Elsewhere in the docs there is a section on singletons which I had not seen:

In Swift, you can simply use a static type property, which is guaranteed to be lazily initialized only once, even when accessed across multiple threads simultaneously:

class Singleton {
    static let sharedInstance = Singleton()
}

If you need to perform additional setup beyond initialization, you can assign the result of the invocation of a closure to the global constant:

class Singleton {
    static let sharedInstance: Singleton = {
        let instance = Singleton()
        // setup code
        return instance
        }()
}