Set the maximum character length of a UITextField in Swift

Question

I know there are other topics on this, but I can't seem to find out how to implement it.

I'm trying to limit a UITextField to only five characters.

Preferably alphanumeric, -, ., and _.

I've seen this code:

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange,                        replacementString string: String) -> Bool {     let maxLength = 4     let currentString: NSString = textField.text     let newString: NSString =              currentString.stringByReplacingCharactersInRange(range, withString: string)     return newString.length <= maxLength } 

and

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {      let length = count(textField.text.utf16) + count(string.utf16) - range.length     return length <= 10 } 

How can I actually implement it? Which "textfield" should I swap out for my custom named UITextField?

Answer 1

1. Your view controller should conform to UITextFieldDelegate, like below:

   class MyViewController: UIViewController, UITextFieldDelegate {  } 

2. Set the delegate of your textfield: myTextField.delegate = self

3. Implement the method in your view controller:

   textField(_:shouldChangeCharactersInRange:replacementString:) 

All together:

class MyViewController: UIViewController, UITextFieldDelegate  // Set delegate to class  @IBOutlet var mytextField: UITextField             //  textfield variable  override func viewDidLoad() {     super.viewDidLoad()     mytextField.delegate = self                  // set delegate }   func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange,                        replacementString string: String) -> Bool {     let maxLength = 4     let currentString: NSString = textField.text     let newString: NSString =              currentString.stringByReplacingCharactersInRange(range, withString: string)     return newString.length <= maxLength } 

For Swift 4

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {     let maxLength = 1     let currentString: NSString = (textField.text ?? "") as NSString     let newString: NSString =         currentString.replacingCharacters(in: range, with: string) as NSString     return newString.length <= maxLength } 

Allowing only a specified set of characters to be entered into a given text field

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {     var result = true      if mytextField == numberField {         if count(string) > 0 {             let disallowedCharacterSet = NSCharacterSet(charactersInString: "0123456789.-").invertedSet             let replacementStringIsLegal = string.rangeOfCharacterFromSet(disallowedCharacterSet) == nil             result = replacementStringIsLegal         }     }     return result } 

How to program an iOS text field that takes only numeric input with a maximum length