How to restrict UITextField to take only numbers in Swift?

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
if let numRange = string.rangeOfCharacterFromSet(NSCharacterSet.letterCharacterSet()) {
return false
} else {
return true
}
}

While most of these solutions will work, be aware that in some localisations a decimals are separated with a "," and not a "."

The cleaner way to do this would be

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
let decimalCharacter = NSNumberFormatter().decimalSeparator
let characterSet = NSMutableCharacterSet.decimalDigitCharacterSet()
characterSet.addCharactersInString(decimalCharacter)

return replacementString.rangeOfCharacterFromSet(characterSet.invertedSet) == nil
}

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
}
}
}

Swift 2.0

For only allowing numbers and one "." decimal in uitextfield.

func textField(textField: UITextField,shouldChangeCharactersInRange range: NSRange,replacementString string: String) -> Bool
{
let newCharacters = NSCharacterSet(charactersInString: string)
let boolIsNumber = NSCharacterSet.decimalDigitCharacterSet().isSupersetOfSet(newCharacters)
if boolIsNumber == true {
return true
} else {
if string == "." {
let countdots = textField.text!.componentsSeparatedByString(".").count - 1
if countdots == 0 {
return true
} else {
if countdots > 0 && string == "." {
return false
} else {
return true
}
}
} else {
return false
}
}
}

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 "."

Swift 2.0

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

let inverseSet = NSCharacterSet(charactersInString:"0123456789").invertedSet

let components = string.componentsSeparatedByCharactersInSet(inverseSet)

let filtered = components.joinWithSeparator("")

return string == filtered

}

First add `delegate` and `keyBoradType` of `textField`

`textField.delegate=self;
textField.keyboardType = UIKeyboardTypeNumberPad;`


Than have to use the `textField.delegate` method like so -

- (BOOL) textField: (UITextField *)theTextField shouldChangeCharactersInRange:(NSRange)range replacementString: (NSString *)string
{
if (!string.length)
{
return YES;
}

if ([string intValue])
{
return YES;
}

return NO;
}

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
// return true if the replacementString only contains numeric characters
let digits = NSCharacterSet.decimalDigitCharacterSet()
for c in string {
if !digits.characterIsMember© {
return false
}
}

return true
}

This solution will work even if the user switches keyboards or tries to paste a non-numeric string into the text field.

Make sure to set the `delegate` property of the appropriate text field.