What is the best way to determine if a string contains a character from a set in Swift

Question

I need to determine if a string contains any of the characters from a custom set that I have defined.

I see from this post that you can use rangeOfString to determine

Answer 1

Swift 3 example:

extension String{
    var isContainsLetters : Bool{
        let letters = CharacterSet.letters
        return self.rangeOfCharacter(from: letters) != nil
    }
}

Usage :

"123".isContainsLetters // false