NSNumberFormatter.numberFromString() returns nil for ar-SA locale

Question

I am trying to format UILabel text for selected locale using NSNumberFormatter for NSNumberFormatterStyle.DecimalStyle and setting up locale for the formatter as ar-SA.

When UILabel text has large numbers that are converted to E notation(scientific notation) for example- "1e9", "2.3456e24" etc. the numberFromString() returns nil for ar-SA locale. However, it works fine for other locales.

@IBOutlet weak var displayText: UILabel!

let format = NSNumberFormatter()
format.numberStyle = NSNumberFormatterStyle.DecimalStyle
format.locale = NSLocale(localeIdentifier: language)// where language = "ar-SA" or "en-US" or "de-DE"
format.maximumFractionDigits = 16  

var result =  displayText.text! // result = "1e9" or "2.3456e24" 
guard let number = format.numberFromString(result), let string = format.stringFromNumber(number) else {
        displayText.text = "Error"
        return
    }
result = string

How to fix this? Is there any restriction with ar-SA locale and E notations together?

Answer 1

You can convert the number to "en" locale and after that you convert the resulting string to "ar_SA" locale. Apparently, the "ar_SA" locale does not recognize the "e" notation.

let format = NSNumberFormatter()
format.numberStyle = NSNumberFormatterStyle.DecimalStyle
format.locale = NSLocale(localeIdentifier: "en")
format.maximumFractionDigits = 16

    var result = displayText.text!
    guard let number = format.numberFromString(result), let string = format.stringFromNumber(number) else {
        return
    }

    format.locale = NSLocale(localeIdentifier: "ar_SA")
    guard let string2 = format.stringFromNumber(number) else {
        return
    }
    result = string2

Answer 2

If you format an NSNumber using an NSNumberFormatter with scientific style and an Arabic locale, you will see that a number such as 2.3456e24 would need to be entered as ٢٫٣٤٥٦اس٢٤.

Trying to parse 2.3456e24 will only work on locales that use the digits 0-9, a period, and e or E for the exponent.

If you wish to allow a user to enter numbers in various formats, you will need to try your number formatter with multiple locales. Start with the default locale. If that gives back a nil number, try another locale. Try as many locales as you wish to support.