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

Updated for Swift 5.1

Question was specifically: "if a string contains any of the characters from a custom set" and not checking for all characters in the custom set.

Using

func check(in string: String, forAnyIn characters: String) -> Bool {
    // create one character set
    let customSet = CharacterSet(charactersIn: characters)
    // use the rangeOfCharacter(from: CharacterSet) function
    return string.rangeOfCharacter(from: customSet) != nil 
}

check(in: "abc", forAnyIn: "A") // false
check(in: "abc", forAnyIn: "b") // true

But this is also very easy to check using character sets.

func check(in string: String, forAnyIn characters: String) -> Bool {
    let customSet = CharacterSet(charactersIn: characters)
    let inputSet = CharacterSet(charactersIn: string)
    return !inputSet.intersection(customSet).isEmpty
}

check(in: "abc", forAnyIn: "A") // false
check(in: "abc", forAnyIn: "b") // true