How to use numberFromString when UITextField has currency value in Swift - ios

Question

I have an 'amount' input field that takes a number value that I wish to display as a currency within the input field itself. This I seem to be able to do with no issues.
I then use this value in a calculation and output as a currency value. Again this works fine the first time as it initially sees it as a double and not currency.
My problem comes when I try and reuse the value in the 'amount' input field, as the value is being seen and no longer a double because of the currency symbol etc.
Any suggestions?
Edited below based on suggestions:
var formatter = NSNumberFormatter()
formatter.numberStyle = NSNumberFormatterStyle.CurrencyStyle
formatter.minimumFractionDigits = 2
formatter.maximumFractionDigits = 2
var numberOfPlaces = 2.0
var multiplier = pow(10, numberOfPlaces)
var enteredAmount = formatter.numberFromString(finalAmount.text)?.doubleValue ?? 0.0
enteredAmountLabel.text = formatter.stringFromNumber(enteredAmount)
finalAmount.text = formatter.stringFromNumber(enteredAmount)
Using these amends the calculations work the first time anything is entered into the field. If you try a calculation when the field is populated it resets the field to $0.00
If I amend to:
formatter.numberStyle = NSNumberFormatterStyle.DecimalStyle
Everything works as expected but the amount input field no longer displays as currency.
I am trying to provide screenshots but I do not have enough reputation points.

Answer 1

Is this the line that gives you trouble?
var enteredAmount = NSNumberFormatter().numberFromString(finalAmount.text)!.doubleValue
It looks like you've got the right idea. You can use a number formatter to convert a value to a formatted string for display, or to convert a formatted string to a value.
I would expect that code to work.
Is that line giving you a compile error? An error at runtime? Not giving the value that it should?
EDIT:
#LeonardoSavioDabus pointed out the problem. That line should use the number formatter you created above:
var enteredAmount = formatter.numberFromString(finalAmount.text)!.doubleValue
And you really shouldn't use force unwrapping like that. You should use the nil coalescing operator:
var enteredAmount = formatter.numberFromString(finalAmount.text)?.doubleValue ?? 0.0
EDIT #2:
Here in the US, this code works perfectly in a playground:
import Foundation
var formatter = NSNumberFormatter()
formatter.numberStyle = NSNumberFormatterStyle.CurrencyStyle
formatter.minimumFractionDigits = 2
formatter.maximumFractionDigits = 2
let moneyString = "$12.93"
var enteredAmount = formatter.numberFromString(moneyString)?.doubleValue ?? 0.0
enteredAmount += 0.07
var newString = formatter.stringFromNumber(enteredAmount)
(I stripped out all the locale stuff to make it simpler.)
EDIT #3:
Your locale code doesn't make sense to me.
for identifier in ["en_US" , "en_UK" , "en_US","fr_FR"] {
formatter.locale = NSLocale(localeIdentifier: identifier)
formatter.minimumFractionDigits = 2
formatter.maximumFractionDigits = 2
}//end of locale detection for currency and decimal formatting
That code looks like it loops through 3 different values of identifier and assigns 3 different locales to your formatter, and the same max/min digit counts (both 2). The way I read that code, it's going to assign first the US locale, then the UK local, then US English again, and then finally French from France. So at the end of the loop the locale will be set to "fr_FR". That's probably not what you want.