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.")
    }

Answer 2

ONE LINE Swift4 solution to check if contains letters:

CharacterSet.letters.isSuperset(of: CharacterSet(charactersIn: myString) // returns BOOL

Another case when you need to validate string for custom char sets. For example if string contains only letters and (for example) dashes and spaces:

let customSet: CharacterSet = [" ", "-"]
let finalSet = CharacterSet.letters.union(customSet)
finalSet.isSuperset(of: CharacterSet(charactersIn: myString)) // BOOL

Hope it helps someone one day:)

Answer 3

Swift 4

let myString = "Some Words"

if myString.contains("Some"){
    print("myString contains the word `Some`")
}else{
    print("myString does NOT contain the word `Some`")
}

Swift 3:

let myString = "Some Words"

if (myString.range(of: "Some") != nil){
    print("myString contains the word `Some`")
}else{
    print("Word does not contain `Some`")
}

Answer 4

You could do it this way:

var string = "Hello, World!"

if string.rangeOfString("W") != nil {
     println("exists")
} else {
     println("doesn't exist")
}

// alternative: not case sensitive
if string.lowercaseString.rangeOfString("w") != nil {
     println("exists")
} else {
     println("doesn't exist")
}

Answer 5

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