How to restrict UITextField to take only numbers in Swift?

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)}

Here is my 2 Cents. (Tested on Swift 2 Only)

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {  let aSet = NSCharacterSet(charactersInString:"0123456789").invertedSet  let compSepByCharInSet = string.componentsSeparatedByCharactersInSet(aSet)  let numberFiltered = compSepByCharInSet.joinWithSeparator("")  return string == numberFiltered}

This is just a little bit more strict. No decimal point either.

Hope it helps :)

PS: I assumed you looked after the delegate anyway.

Update: Swift 3.0 :

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {    let aSet = NSCharacterSet(charactersIn:"0123456789").inverted    let compSepByCharInSet = string.components(separatedBy: aSet)    let numberFiltered = compSepByCharInSet.joined(separator: "")    return string == numberFiltered}

In swift 4.1 and Xcode 9.4.1

Add UITextFieldDelegate to your class

class YourViewController: UIViewController, UITextFieldDelegate

Then write this code in your viewDidLoad()

mobileNoTF.delegate = self

Write this textfield delegate function

//MARK - UITextField Delegatesfunc textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {    //For mobile numer validation    if textField == mobileNoTF {        let allowedCharacters = CharacterSet(charactersIn:"+0123456789 ")//Here change this characters based on your requirement        let characterSet = CharacterSet(charactersIn: string)        return allowedCharacters.isSuperset(of: characterSet)    }    return true}