XCode 8上的Swift 3 Playground“对成员'joined（）'的引用不正确

Question

I have the Dictionary:

let alphabet: [Character: Int] = ["a": 0, "b": 1, "c": 2, "d": 3]

let validSet = CharacterSet.init(charactersIn: alphabet.keys.joined())

and that's when I get the error. How could I fix this and Why is it happening? Any ideas?

Answer 1

If you don't want to change your key type to String as already suggested, then map the Characters to Strings:

let alphabet: [Character: Int] = ["a": 0, "b": 1, "c": 2, "d": 3]
let validSet = CharacterSet(charactersIn: alphabet.keys.map{String($0)}.joined())

Answer 2

The only thing you should change to make it work is the type of keys, from Character to String :

let alphabet: [String: Int] = ["a": 0, "b": 1, "c": 2, "d": 3]
let validSet = CharacterSet.init(charactersIn: alphabet.keys.joined())