Swift String extension checking if String contains letters or digits

String+contains.swift

import Foundation

extension String {
    var containsOnlyDigits: Bool {
        let notDigits = NSCharacterSet.decimalDigits.inverted
        return rangeOfCharacter(from: notDigits, options: String.CompareOptions.literal, range: nil) == nil
    }
    
    var containsOnlyLetters: Bool {
        let notLetters = NSCharacterSet.letters.inverted
        return rangeOfCharacter(from: notLetters, options: String.CompareOptions.literal, range: nil) == nil
    }
    
    var isAlphanumeric: Bool {
        let notAlphanumeric = NSCharacterSet.decimalDigits.union(NSCharacterSet.letters).inverted
        return rangeOfCharacter(from: notAlphanumeric, options: String.CompareOptions.literal, range: nil) == nil
    }
}

Thanks