How to Keep Static Prefix in UITextField When Pasting String - uitextfield

Question

I have a UITextField that handles input of currency. The initial state of the text field has a set value of $0.00 but changes to just $ when it becomes the first responder.
I have successfully disabled the user from deleting the $ prefix of the text field's text by adding this:
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
if textField == priceTextField {
if range.length == 1 && count(string) == 0 {
// Deleting text
if range.location <= 0 {
return false
}
}
}
return true
}
However, this only works when the user enters text with keys and then deletes text by pressing the backspace key. If the user copies text, highlights the $ prefix and then pastes in the text, the $ prefix gets replaced with the pasted text.
If the user selects the location before the $ prefix and pastes the text, I move the $ prefix to the replacement string by handling it with:
if range.location == 0 && count(string) >= 1 {
textField.text = "$\(string)"
return false
}
I realize that I need to create some logic for using the range of the text in the text field, but I'm not sure about where to start.
I'm not asking for a handout of a code snippet, but rather if someone can point me in the direction of what sort of logic I am needing to implement so that the $ prefix is not editable and always at the beginning of the text (even when selected and pasted over)?

Answer 1

I would suggest you to,
1.If textfield is empty, use placeholder property of UITextField to indicate what needs to be entered.
2.If the textfield has a value,
i) in textFieldDidBeginEditing delegate, remove the $ symbol from the value, i.e. when textfield is active.
ii) in textFieldDidEndEditing delegate, add the $ symbol to the value entered, i.e. when textfield is inactive.