UITextField — Restrict textfield to a certain character (iOS)

If you want to perform a user input validation of your textfield use the following code snippet:

// MARK: - UITextFieldDelegatelet allowedCharacters = CharacterSet(charactersIn:”0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvxyz”).invertedfunc textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {let components = string.components(separatedBy: allowedCharacters)
    let filtered = components.joined(separator: "")if string == filtered {
        return true} else {
        return false  } 
}

Objective-C

#define ACCEPTABLE_CHARACTERS @”0123456789 ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz”- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
 {NSCharacterSet *cs = [[NSCharacterSet
characterSetWithCharactersInString:ACCEPTABLE_CHARACTERS] invertedSet];NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs]
componentsJoinedByString:@""];return [string isEqualToString:filtered];
}

In addition you can also use character sets provided by apple to perform validation:

Take a look at https://developer.apple.com/reference/foundation/nscharacterset

let allowedCharacters = CharacterSet.alphanumerics.inverted
let allowedCharacters = CharacterSet.capitalizedLetters.inverted