Add a prefix to UITextField

Question

I want a \'$\' Sign in the text field which cannot be erased. A user should be able to enter values after it and if he presses backspace it should only erase the value he entere

Answer 1

You can subclass UITextField for all the text field which take amount as value.

class SpecialTextField: UITextField {

var amount: String {
    get {
        if self._amount.characters.count > 1 {
            return (self._amount as NSString).substringFromIndex(2)
        }
        return ""
    }
}

// MARK: - UITextField Observing
override internal func willMoveToSuperview(newSuperview: UIView!) {
    if newSuperview != nil {
        keyboardType = .DecimalPad
        addTarget(self, action: #selector(SpecialTextField.didChangeText), forControlEvents: .EditingChanged)
    }
}

override internal func canPerformAction(action: Selector, withSender sender: AnyObject?) -> Bool {
    return false
}


private var newVal: String = ""
private var _amount: String = ""

func didChangeText() {
    if (text?.characters.count > 2) {
        if text?.rangeOfString("$ ") == nil {
            text = newVal
        }
    }

    if (text?.characters.count == 1) && (text?.characters.count > newVal.characters.count) {
        text = "$ " + text!
    }
    if (text?.characters.count == 2) && (text?.characters.count < newVal.characters.count) {
        text = ""
    }
    newVal = text ?? ""
    _amount = newVal
}
}

This will insert a $ sign whenever first number is entered, and removes it whenever all the numbers are removed.

var amount will give the actual amount value user has entered, after removing the $ sign.

Hope this helped.