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

Using Swift 3 to determine if your string contains characters from a specific CharacterSet:

    let letters = CharacterSet.alphanumerics
    let string = "my-string_"
    if (string.trimmingCharacters(in: letters) != "") {
        print("Invalid characters in string.")
    }
    else {
        print("Only letters and numbers.")
    }