How to limit number of decimals in textfield when user input is from pasteboard, iOS Swift

Question

I have a textfield where user can input only 6 decimals, if there are decimals, if there aren't then he is allowed to input as many characters as user wants.

For example, I am allowing this: 7472828282 and this: 0,123456, not this: 0,2139213773219312.

And my current implementation is ok with this examples above and when user is making input from ekeyboard, but I can't manage to make it work when user pastes some value, for example user can paste this value: 0,123456789, but I would like to cut it after 6th decimal, to be actually like this: 0,123456, and no, I don't need to round it on bigger decimal, I need to cut it!

Thanks for help, my so far code is below

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
if textField === self.amountView.textField {
    
    guard let text = textField.text, let decimalSeparator = NSLocale.current.decimalSeparator else {
        return true
    }
    
    var splitText = text.components(separatedBy: decimalSeparator)
    let totalDecimalSeparators = splitText.count - 1
    let isEditingEnd = (text.count - 3) < range.lowerBound
    
    splitText.removeFirst()
    
    if  splitText.last?.count ?? 0 > 5 && string.count != 0 && isEditingEnd {
        return false
    }
    
    if totalDecimalSeparators > 0 && string == decimalSeparator {
        return false
    }
}
return true
}

Answer 1

This code always updates the content of textField but limits the number of decimals:

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

    guard let decimalSeparator = NSLocale.current.decimalSeparator else {return true}

    // Updates the text
    var updatedText = (textView.text as NSString).replacingCharacters(in: range, with: text) 

    // If someone needs to cover all possible decimal separator values, the commented line below is the solution
    // let textComponents = updatedText.components(separatedBy: [",", "."])

    let textComponents = updatedText.components(separatedBy: decimalSeparator)
    
    // Truncates the decimals
    if textComponents.count > 1 && textComponents[1].count > 6{
       updatedText = textComponents[0].appending(decimalSeparator).appending((textComponents[1] as NSString).substring(to: 6))
    }
        
    textView.text = updatedText

    // The text has already been updated, so returns false
    return false 
}

Answer 2

Your mistake: You are checking the old content.

shouldChangeCharacters gives you the old text (still in the text field), a range to be replaced (selection or just insertion point) and replacement. You first need to calculate the new text if the range was replaced, and then check that result.