Convert Swift Set to NSMutableSet

Question

I can convert from NSMutableSet to Set no problem, but I'm running into problems when doing the reverse.

E.g. this works:

let nsSet = NSMutableSet(array: ["a", "b"])
let swiftSet = nsSet as! Set<String>

But when I try:

let nsSet2 = swiftSet as? NSMutableSet

nsSet2 ends up being nil.

Peruse

Don't do that. Don't use NSMutable... collection types in Swift at all. Set with var is mutable for free (and type safe). – Funches

@Funches needed to store in NSUserDefaults, for example – Peruse

I doubt that. NS(Mutable)Set is not a property list compliant type – Funches

@vadian: yup, you're right. Turns out I was looking at NSKeyValueCoding methods instead. – Peruse

Answer 1

Looks like swift Sets need to be converted to NSSet first:

let nsSet2 = NSMutableSet(set: set as NSSet)

Or shorthand:

let nsSet2 = NSMutableSet(set: set)

Or to go from NSSet to Swift Set and back to NSSet:

let nsSet = NSMutableSet(array: ["a", "b"])
let set = nsSet as! Set<String>
let nsSet2 = set as NSSet
let nsSet3 = NSMutableSet(set: nsSet2)

Peruse