How to do a live UITextField count while typing (Swift)?

A very elegant and neat solution exists using UITextFieldDelegate. My solution uses the concept of selectors. In a selector you tell your compiler what function/action to perform when a particular event happens. In this case - typing in textfield. Make sure that you have set the textField delegate in storyboard.

override func viewDidLoad() {
   super.viewDidLoad()
   yourTextField.addTarget(self, action: #selector(YourViewController.textFieldDidChange(_:)), for: UIControlEvents.EditingChanged)
}

@objc func textFieldDidChange(textField : UITextField){
   label.text = yourTextField.text?.count
}

To use the function below you need to implement the UITextFieldDelegate protocol on the text field you want to count. This gets called every time the UITextFields text changes:

Your class declaration should look something like this

class ViewController: UIViewController, UITextFieldDelegate

You should have an @IBOutlet similar to this

@IBOutlet var txtValue: UITextField

Set the UITextField s delegate to self.

override func viewDidLoad() {
    super.viewDidLoad()
    txtValue.delegate = self                
}

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

    mylabel.text =  String(newLength) // Set value of the label
    // myCounter = newLength // Optional: Save this value
    // return newLength <= 25 // Optional: Set limits on input. 
    return true
}

Note that this function is called on all UITextFields so if you have several UITextFields you will need to add a logic to know witch one is calling this function.

For multiple UITextView

class ViewController: UIViewController, UITextViewDelegate {

 @IBOutlet weak var ticketSummaryTV: UITextView!
 @IBOutlet weak var ticketDescriptionTV: UITextView!

 @IBOutlet weak var summaryCountLbl: UILabel!
 @IBOutlet weak var descriptionCountLbl: UILabel!

 override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.

    ticketSummaryTV.delegate = self
    ticketDescriptionTV.delegate = self

    self.updateCharacterCount()
 }

 func updateCharacterCount() {
    let summaryCount = self.ticketSummaryTV.text.characters.count
    let descriptionCount = self.ticketDescriptionTV.text.characters.count

    self.summaryCountLbl.text = "\((0) + summaryCount)/50"

    self.descriptionCountLbl.text = "\((0) + descriptionCount)/500"
 }

 func textViewDidChange(_ textView: UITextView) {
    self.updateCharacterCount()
 }


 func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool{
    if(textView == ticketSummaryTV){
       return textView.text.characters.count +  (text.characters.count - range.length) <= 50
    }else if(textView == ticketDescriptionTV){
        return textView.text.characters.count +  (text.characters.count - range.length) <= 500
    }
    return false
 }
}