将 Swift 集转换为 NSMutableSet

Question

我可以从 NSMutableSet 转换为 Set 没问题，但我在做相反的事情时遇到了问题。

例如这有效：

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

但是当我尝试：

let nsSet2 = swiftSet as? NSMutableSet

nsSet2最终成为nil.

Answer 1

看起来需要先将 swift Sets 转换为 NSSet ：

let nsSet2 = NSMutableSet(set: set as NSSet)

或简写：

let nsSet2 = NSMutableSet(set: set)

或者从 NSSet 到 Swift Set 再回到 NSSet：

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