How to allow dot or comma in UITextField in calculation? - swift

Question

I am newbie in coding. I just started to learn #swift and trying yo make a calculation app. My problem is my UITextField doesn't work with dot or comma.
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var ilkLabel: UITextField!
#IBOutlet weak var ikinciLabel: UITextField!
#IBOutlet weak var sonucLabel: UILabel!
#IBOutlet weak var ilk2Label: UITextField!
#IBOutlet weak var ikinci2Label: UITextField!
#IBOutlet weak var sonuc2Label: UILabel!
#IBOutlet weak var ilk3Label: UITextField!
#IBOutlet weak var ikinci3Label: UITextField!
#IBOutlet weak var sonuc3Label: UILabel!
var sonuc:Double = 0
var sonuc2:Double = 0
var sonuc3:Double = 0
var deneme:Double = 0
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
self.view.endEditing(true)
}
#IBAction func plusBtn(_ sender: Any) {
func forTrailingZero(temp: Double) -> String {
let tempVar = String(format: "%g", temp)
return tempVar
}
deneme = Double(Int(ikinciLabel.text!)! + 100 / 100 * Int(ilkLabel.text!)!)
sonucLabel.text = String(forTrailingZero(temp: Double(ikinciLabel.text!)! / 14.56 ) )
}
#IBAction func plus2Btn(_ sender: Any) {
}
#IBAction func plus3Btn(_ sender: Any) {
}
}
I expect to make calculation like 1.4 + 2.35 but when i try the app crashes. I can only calculate whole number like 2 + 2.

Answer 1

#matt is right. If the text in ikinciLabel is not an Int, the app crashes. You tell it to crash by using the force unwrap operator: !.
In general
You should only force-unwrap things when you are absolutely sure that the thing you want to unwrap is not nill. In all other cases you should if-let or guard-let the optional, use the nil-coalescing operator (??) (or other ways to unwrap optionals) and handle the nil-case.
In your case
if you want to allow the user to enter floating point numbers using either a comma or a dot, you could simply replace every comma with a dot like so:
let enteredTextWithoutComma = textField.text?.replacingOccurrences(of: ",", with: ".")
This new constant is an optional. To safely make a Double out of it, do:
guard let enteredTextWithoutCommaUnwraped = enteredTextWithoutComma,
let enteredNumber = Double(enteredTextWithoutCommaUnwraped) else {
// one of the two actions didn't work. Maybe the entered phrase was not a number
// do something
return
}
// here you can use the variable enteredNumber. It is now a Double (not an Optional)
...