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

Swift 5.3

In some version its changed and now it says:

When the user deletes one or more characters, the replacement string is empty.

So answer for this:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
  if string.isEmpty {
    // do something
  }
  return true
}

If you want to detect that some characters will be deleted

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
  if range.length > 0 {
    // We convert string to NSString instead of NSRange to Range<Int>
    // because NSRange and NSString not counts emoji as one character
    let replacedCharacters = (string as NSString).substring(with: range)
  }
  return true
}

If you want detect backspaces even on empty textField

class TextField: UITextField {
  var backspaceCalled: (()->())?
  override func deleteBackward() {
    super.deleteBackward()
    backspaceCalled?()
  }
}

Old answer

Please don't trash your code. Just put this extension somewhere in your code.

extension String {
  var isBackspace: Bool {
    let char = self.cString(using: String.Encoding.utf8)!
    return strcmp(char, "\\b") == -92
  }
}

And then just use it in your functions

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
  if string.isBackspace {
    // do something
  }
  return true
}

Answer 2

Swift 4: If the user presses the backspace button, string is empty so this approach forces textField to only accept characters from a specified character set (in this case utf8 characters) and backspaces (string.isEmpty case).

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    if string.cString(using: String.Encoding.utf8) != nil {
        return true
    } else if string.isEmpty {
        return true
    } else {
        return false
    }
}

Answer 3

In Swift 3

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let  char = string.cString(using: String.Encoding.utf8)!
    let isBackSpace = strcmp(char, "\\b")

    if (isBackSpace == -92) {
         print("Backspace was pressed")
    }
    return true
}

:)

Answer 4

Try this

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

if(string == "") {

        print("Backspace pressed");
        return true;
    }
}

Note: You can return "true" if you want to allow backspace. Else you can return "false".

Answer 5

Swift 4

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

    //MARK:- If Delete button click
    let  char = string.cString(using: String.Encoding.utf8)!
    let isBackSpace = strcmp(char, "\\b")

    if (isBackSpace == -92) {
        print("Backspace was pressed")

        return true
    }
}