How to prevent users from entering '#' and empty space(' ') in UITextfield - swift? - ios

Question

I am trying to prevent users from entering the characters '#' and empty spaces (' '). I have got as far as below (see code below) but not sure how to complete the rest ...
class CreateTags: UIViewController, UITextFieldDelegate {
/*** OUTLETS ***/
#IBOutlet weak var inputTxtOutlet: UITextField!
override func viewDidLoad() {
self.inputTxtOutlet.delegate = self
}
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
return true
}
}

Answer 1

You need o implement following delegate method (as you already implemented)
Set delegate
yourtextField.delegate = self
Delegate method
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
if string == "#" || string == " " {
return false //disallow # and a space
}
return true
}
In another way you can do it as follow
Create a constant that contains disallowed chars.
let disallowedChars = ["#", " "] //add more chars as per your need
In delegate method check those chars...
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
if disallowedChars.contains(string) {
return false
}
return true
}

Answer 2

Try to be specific for UITextfields!
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
if textField == inputTxtOutlet {
let myCharSet = CharacterSet(charactersIn:" #")
let output: String = string.trimmingCharacters(in: myCharSet.inverted)
let isValid: Bool = (string == output)
if isValid {
return false
} else {
return true
}
}
return true
}

Answer 3

let restrictedChars = ["#", "*", " "]
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
return restrictedChars.contains(string) ? false : true
}

Answer 4

Here is a one-liner. (Works for copy paste!)
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
return !string.contains(where: {$0 == "#" || $0 == " "})
}
If you have a lot of restricted characters,
let restrictedCharacters: [Character] = [" ", "#", "?"]
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
return !(Set(string).intersection(Set(restrictedCharacters)).count > 0)
}

Answer 5

Here is your solution:-
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
let characters = ["#", "$", "!", "&","#"]
for character in characters{
if string == character{
print("This characters are not allowed")
return false
}
}
}
uses this How to restrict certain characters in UITextField in Swift? example

Answer 6

extension String {
var containsValidCharacter: Bool {
guard self != "" else { return true }
let hexSet = CharacterSet(charactersIn: "1234567890ABCDEFabcdef")
let newSet = CharacterSet(charactersIn: self)
return hexSet.isSuperset(of: newSet)
}
}
You use it like with the UITextFieldDelegate.
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
return (string.containsValidCharacter)
}

Answer 7

Replace Your "shouldChangeCharactersIn" method with below code
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
let characters = ["#", " "]
for character in characters{
if string == character{
print("This characters are not allowed")
return false
}
}
return true
}