swift - 将 Swift Set 转换为 NSMutableSet

Question

我可以从 NSMutableSet 转换为 Set 没问题，但在执行相反操作时我遇到了问题。

例如这有效:

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

但是当我尝试时:

let nsSet2 = swiftSet as? NSMutableSet

nsSet2 最终为 nil。

Answer 1

看起来 swift Sets 需要先转换为 NSSet:

let nsSet2 = NSMutableSet(set: set as NSSet)

或速记:

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)