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 delegate for the UITextField and set it to self

self.textField.delegate = self;

Then I know to use shouldChangeCharactersInRange delegate method to detect if a backspace was pressed is all code are in Objective-C. I need in Swift these following method as below is used.

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    const char * _char = [string cStringUsingEncoding:NSUTF8StringEncoding];
    int isBackSpace = strcmp(_char, "\b");

    if (isBackSpace == -8) {
        // NSLog(@"Backspace was pressed");
    }

    return YES;
}

Answer 1

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
    }
}

Answer 2

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

Swift 5.1

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 3

Swift 4

func textField(_ textField: UITextField, shouldChangeCharactersIn 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 false
            }
}

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

I implemented this feature:

And in the case where the last textFiled is empty, I just want to switch to the previous textFiled. I tried all of the answers above, but no one works fine in my situation. For some reason, if I add more logic than print in isBackSpace == -92 parentheses block this method just stopped work...

As for me the method below more elegant and works like a charm:

Swift

class YourTextField: UITextField {

    // MARK: Life cycle

    override func awakeFromNib() {
        super.awakeFromNib()
    }

    // MARK: Methods

    override func deleteBackward() {
        super.deleteBackward()

        print("deleteBackward")
    }

}

Thanks @LombaX for the answer