Detect backspace Event in UITextField

Question

I am searching for solutions on how to capture a backspace event, most Stack Overflow answers are in Objective-C but I need on Swift language.

First I have set deleg

Answer 1

If u need detect backspace even in empty textField (for example in case if u need auto switch back to prev textField on backSpace pressing), u can use combination of proposed methods - add invisible sign and use standard delegate method textField:shouldChangeCharactersInRange:replacementString: like follow

1. Create invisible sign

   private struct Constants {
       static let InvisibleSign = "\u{200B}"
   }
   

2. Set delegate for textField

   textField.delegate = self
   

3. On event EditingChanged check text and if needed add invisible symbol like follow:

   @IBAction func didChangeEditingInTextField(sender: UITextField) {
       if var text = sender.text {
           if text.characters.count == 1 && text != Constants.InvisibleSign {
               text = Constants.InvisibleSign.stringByAppendingString(text)
               sender.text = text
           }
       }
   }
   

4. Add implementation of delegate method textField:shouldChangeCharactersInRange:replacementString:

   extension UIViewController : UITextFieldDelegate {
       // MARK: - UITextFieldDelegate
       func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
   
           let  char = string.cStringUsingEncoding(NSUTF8StringEncoding)!
           let isBackSpace = strcmp(char, "\\b")
   
           if (isBackSpace == -92) {
               if var string = textField.text {
                   string = string.stringByReplacingOccurrencesOfString(Constants.InvisibleSign, withString: "")
                   if string.characters.count == 1 {
                       //last visible character, if needed u can skip replacement and detect once even in empty text field
                       //for example u can switch to prev textField 
                       //do stuff here                            
                   }
               }
           }
           return true
       }
   }