Format currency in textfield in Swift on input

Question

I am trying to format currency input in a textfield in Swift as the user inputs it.

So far, I can only format it successfully when the user finishes inputting:

@IBAction func editingEnded(sender: AnyObject) {

    let formatter = NSNumberFormatter()
    formatter.numberStyle = NSNumberFormatterStyle.CurrencyStyle
    formatter.locale = NSLocale(localeIdentifier: "en_US")
    var numberFromField = NSString(string: textField.text).doubleValue

    textField.text = formatter.stringFromNumber(numberFromField)
}

However, I would like for the currency to be formatted the moment the user inputs it. When I try to do it on the TextField actions "Editing Changed" or "Value Changed", I can only enter 1 number (if I enter 8, it becomes $8.00) but then once I enter a second number everything goes to $0.00 and I cannot enter further beyond that.

Any suggestions? I feel like this should be an easy fix but I can't quite get at it.

Answer 1

I modified the function from earlier today. Works great for "en_US" and "fr_FR". However, for "ja_JP", the division by 100 I do to create decimals is a problem. You will need to have a switch or if/else statement that separates currencies with decimals and those that do not have them when formatted by the formatter. But I think this gets you in the space you wanted to be.

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {

    @IBOutlet weak var textField: UITextField!
    var currentString = ""

    override func viewDidLoad() {
        super.viewDidLoad()

        self.textField.delegate = self
    }

    //Textfield delegates
    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool { // return NO to not change text

        switch string {
        case "0","1","2","3","4","5","6","7","8","9":
            currentString += string
            println(currentString)
            formatCurrency(string: currentString)
        default:
            var array = Array(string)
            var currentStringArray = Array(currentString)
            if array.count == 0 && currentStringArray.count != 0 {
                currentStringArray.removeLast()
                currentString = ""
                for character in currentStringArray {
                    currentString += String(character)
                }
                formatCurrency(string: currentString)
            }
        }
        return false
    }

    func formatCurrency(#string: String) {
        println("format \(string)")
        let formatter = NSNumberFormatter()
        formatter.numberStyle = NSNumberFormatterStyle.CurrencyStyle
        formatter.locale = NSLocale(localeIdentifier: "en_US")
        var numberFromField = (NSString(string: currentString).doubleValue)/100
        textField.text = formatter.stringFromNumber(numberFromField)
        println(textField.text )
    }
}

Answer 2

this works for me using NSNumberFormatter...

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

    // Construct the text that will be in the field if this change is accepted
    var 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.numberStyle = NSNumberFormatterStyle.CurrencyStyle
    formatter.locale = NSLocale(localeIdentifier: "en_US")
    var numberFromField = (NSString(string: digitText).doubleValue)/100
    newText = formatter.stringFromNumber(numberFromField)

    textField.text = newText

    return false
}

Answer 3

Based on @Robert answer. Updated for Swift 2.0

//Textfield delegates
func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool { // return NO to not change text

    switch string {
    case "0","1","2","3","4","5","6","7","8","9":
        currentString += string
        formatCurrency(currentString)
    default:
        if string.characters.count == 0 && currentString.characters.count != 0 {
            currentString = String(currentString.characters.dropLast())
            formatCurrency(currentString)
        }
    }
    return false
}

func formatCurrency(string: String) {
    print("format \(string)")
    let formatter = NSNumberFormatter()
    formatter.numberStyle = NSNumberFormatterStyle.CurrencyStyle
    formatter.locale = NSLocale(localeIdentifier: "en_US")
    let numberFromField = (NSString(string: currentString).doubleValue)/100
    self.amountField.text = formatter.stringFromNumber(numberFromField)
    print(self.amountField.text )
}