Swift: Add comma and $ in the textfield when typing - swift

Question

I want the users see the $ and comma when they are typing in a textfield from numberPad (Without a decimal dot). Previously I got help and use below codes. But clients will not type the decimal (Only Int value).
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
let oldText = textField.text! as NSString
var newText = oldText.stringByReplacingCharactersInRange(range, withString: string) as NSString!
var newTextString = String(newText)
let digits = NSCharacterSet.decimalDigitCharacterSet()
var digitText = ""
for c in newTextString.unicodeScalars {
if digits.longCharacterIsMember(c.value) {
digitText.append(c)
}
}
let formatter = NSNumberFormatter()
// formatter.usesSignificantDigits = false
formatter.numberStyle = NSNumberFormatterStyle.CurrencyStyle
formatter.locale = NSLocale(localeIdentifier: "en_US")
let numberFromField = (NSString(string: digitText).doubleValue) / 100
newText = formatter.stringFromNumber(numberFromField)
textField.text = String(newText)
return false
}
When typing, it always starts from the second decimal unit, How to remove the ".00" via editing the code and let it start from the unit? I tried for a long time, thanks in advance.

Answer 1

First, you got some bad advice. You should not be using shouldChangeCharactersInRange to change the characters in a text field. That's for checking if the characters typed are valid for the field. The only thing you should do in this method is return true if the user entered digits or delete, otherwise false. (Remember, the user may be using an external keyboard so just having the keypad up isn't good enough to stop non-digit entry.)
Instead you should be using an #IBAction connected to the field's EditingChanged event. Inside this method is where you should update the text.
#IBAction func editingChanged(sender: UITextField) {
let digits = sender.text?.digitsOnly ?? "0"
sender.text = "$\(digits).00" // If I understand what you want.
}
The below extension should be somewhere in your code base. It's generally useful so store it in a gist or something, you will likely need it in future projects.
extension String {
var digitsOnly: String {
return componentsSeparatedByCharactersInSet(NSCharacterSet.decimalDigitCharacterSet().invertedSet).joinWithSeparator("")
}
}
You have to make sure that the IBAction is attached to the EditingChanged event:
For Swift 4x
extension String {
var digitsOnly: String {
return components(separatedBy: NSCharacterSet.decimalDigits.inverted).joined(separator: "")
}
}