Displaying and Updating Currency in a UILabel

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Setup

 1import UIKit
 2import PlaygroundSupport
 3
 4class MyViewController : UIViewController {
 5    
 6    var currencyLabel = UILabel()
 7    override func loadView() {
 8        let view = UIView()
 9        view.backgroundColor = .white
10
11        currencyLabel.frame = CGRect(x: 150, y: 200, width: 200, height: 20)
12        currencyLabel.text = "$0.00"
13        currencyLabel.textColor = .black
14        
15        view.addSubview(currencyLabel)
16        self.view = view
17    }
18}
19
20let viewController = MyViewController()
21PlaygroundPage.current.liveView = viewController

Live View Starting Label Value

Exract the current currency value from the label

Chances are, you’re displaying whatever currency value you’re displaying as a String in your user interface. Therefore, you need to extract it out of whatever UI element you’re displaying it in, and get it ready to do “number stuff” with…

1let currentTotalString = viewController.currencyLabel.text?.replacingOccurrences(of: "$", with: "", options: String.CompareOptions.literal, range: nil)
2
3var currentTotal = NSDecimalNumber(string: currentTotalString)

0

Make a random currency amount to add to the current total

For this example, create a random number to between 0 and 5 to test out adding some amount to the current total.

1let randomRange = Range<Double>(uncheckedBounds: (0.0,5.0))
2let randomAmount = Double.random(in: randomRange)
3let amountToAdd = NSDecimalNumber(floatLiteral: randomAmount)

2.095023084295587 // Output from my Playground run

Add to the current total

1currentTotal = currentTotal.adding(amountToAdd)

2.095023084295587 // Output from my Playground run

Make a currency formatter, format as currency, and update the UI

The way to format numbers as currency is with a NumberFormatter. I’m keeping it simple in this example, but there are various customization points available to you.

1let currencyFormatter = NumberFormatter()
2currencyFormatter.locale = Locale.current
3currencyFormatter.usesGroupingSeparator = true
4currencyFormatter.numberStyle = NumberFormatter.Style.currency
5
6viewController.currencyLabel.text = currencyFormatter.string(from: currentTotal)

Live View Ending Label Value

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