How to restrict UITextField to take only numbers in Swift?

Question

I want the user to only enter numeric values in a UITextField. On iPhone we can show the numeric keyboard, but on iPad the user can switch to any keyboard.

Answer 1

Use number formatter

Swift 4.x

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
      let s = NSString(string: textField.text ?? "").replacingCharacters(in: range, with: string)
      guard !s.isEmpty else { return true }
      let numberFormatter = NumberFormatter()
      numberFormatter.numberStyle = .none
      return numberFormatter.number(from: s)?.intValue != nil
 }

Answer 2

Solution for swift 3.0 and above

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool
  {
    let allowedCharacters = CharacterSet.decimalDigits
    let characterSet = CharacterSet(charactersIn: string)
    return allowedCharacters.isSuperset(of: characterSet)
  }

Answer 3

This is a more readable version that will do "0-9" plus ".":

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {

    let existingTextHasDecimal = textField.text?.rangeOfString(".")
    let replacementTextHasDecimal = string.rangeOfString(".")
    let replacementTextAllCharacters = NSCharacterSet(charactersInString: string)
    let replacementTextOnlyDigits = NSCharacterSet.decimalDigitCharacterSet().isSupersetOfSet(replacementTextAllCharacters)

    if replacementTextHasDecimal != nil && existingTextHasDecimal != nil {
        return false
    }else{
        if replacementTextOnlyDigits == true {
            return true
        }else if replacementTextHasDecimal != nil{
            return true
        }else{
            return false
        }
    }
}

Answer 4

I had actually done this when working through the Big Nerd Ranch book, my solution is:

func textField(textField: UITextField, 
    shouldChangeCharactersInRange range: NSRange, 
    replacementString string: String) -> Bool {

    let newCharacters = NSCharacterSet(charactersInString: string)
    return NSCharacterSet.decimalDigitCharacterSet().isSupersetOfSet(newCharacters)
}

this only allows the numbers 0-9, to allow the "." as well is more complicated as you can only allow one "."

Answer 5

I think you can force change the keyboard type by implementing UITextInputTraits protocol, optional var keyboardType

//class ViewController: UIViewController, UITextInputTraits {

@IBOutlet weak var textFieldKeyboardType: UITextField!{
    didSet{
        textFieldKeyboardType.keyboardType = UIKeyboardType.NumberPad
    }
}
var keyboardType: UIKeyboardType { 
    get{ 
        return textFieldKeyboardType.keyboardType
    } 
    set{ 
        if newValue != UIKeyboardType.NumberPad{
            self.keyboardType = UIKeyboardType.NumberPad
        }
    } 
}

Answer 6

I have edited Raj Joshi's version to allow one dot or one comma:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    let inverseSet = CharacterSet(charactersIn:"0123456789").inverted
    let components = string.components(separatedBy: inverseSet)
    let filtered = components.joined(separator: "")

    if filtered == string {
        return true
    } else {
        if string == "." || string == "," {
            let countDots = textField.text!.components(separatedBy:".").count - 1
            let countCommas = textField.text!.components(separatedBy:",").count - 1

            if countDots == 0 && countCommas == 0 {
                return true
            } else {
                return false
            }
        } else  {
            return false
        }
    }
}