Check if a UITextField is characters/numbers only - ios

Question

I have this block of code....
let characterset = CharacterSet(charactersIn: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-")
if itemDescription.text!.rangeOfCharacter(from: characterset.inverted) != nil {
print("string contains special characters")
let message = MDCSnackbarMessage()
message.text = "Numbers and letters only."
MDCSnackbarManager.show(message)
progressView.isHidden = true
buttonSearchOutlet.isHidden = false
}
No matter what I type in, I get the snackbar to show. I expect these to be false
Hello
hello
hello1
hello-
I expect this to be true
Hello!
hello's
hello1#
hello$&##
What did I do wrong?

Answer 1

You can simply check if all characters satisfy a condition and check if your string with the valid characters contais those characters.
extension StringProtocol {
var isLetterDigitOrHyphen: Bool {
allSatisfy("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-".contains)
}
}
Usage:
let str = "Hello"
if str.isLetterDigitOrHyphen {
print("string is ok")
} else {
print("string contains special characters")
}
"Hello".isLetterDigitOrHyphen // true
"hello".isLetterDigitOrHyphen // true
"hello1".isLetterDigitOrHyphen // true
"hello-".isLetterDigitOrHyphen // true
"Hello!".isLetterDigitOrHyphen // false
"hello's".isLetterDigitOrHyphen // false
"hello1#".isLetterDigitOrHyphen // false
"hello$&##".isLetterDigitOrHyphen // false
If you would like to use regular expressions:
extension StringProtocol {
var isLetterDigitOrHyphen: Bool {
range(of:"^[a-zA-Z0-9-]{1,}$", options: .regularExpression) != nil
}
}
Or using a character set:
extension StringProtocol {
var isLetterDigitOrHyphen: Bool {
unicodeScalars.allSatisfy(CharacterSet(charactersIn: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-").contains)
}
}
Of course you can simply negate the result if you would like to:
extension String {
static let validCharacters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-"
}
extension StringProtocol {
var isNotLetterDigitOrHyphen: Bool {
!unicodeScalars.allSatisfy(CharacterSet(charactersIn: .validCharacters).contains)
}
}