I'm creating a simple calculator app and currently struggling at deleting the last character when a my button is tapped. I'm using the dropLast() method but I keep getting the error
Missing Argument for parameter #1 in call
@IBAction func onDelPressed (button: UIButton!) { runningNumber = runningNumber.characters.dropLast() currentLbl.text = runningNumber } In Swift, you can apply dropLast() directectly on the String instance, no longer invoking .characters to access a CharacterView of the String:
var runningNumber = "12345" runningNumber = String(runningNumber.dropLast()) print(runningNumber) // 1234 I'll assume runningNumber is a String instance. In this case, runningNumber.characters.dropLast() is not of type String, but a CharacterView:
let foo = runningNumber.characters.dropLast() print(type(of: foo)) // CharacterView You need to use the CharacterView to instantiate a String instance prior to assigning it back to a property of type String, e.g.
var runningNumber = "12345" runningNumber = String(runningNumber.characters.dropLast()) print(runningNumber) // 1234 I.e., for your case
@IBAction func onDelPressed (button: UIButton!) { runningNumber = String(runningNumber.characters.dropLast()) currentLbl.text = runningNumber } 
String instance (e.g. runningNumber) is only of a single Character or is empty (""), the resulting String instance after applying dropLast to the CharacterView of it will be an empty String (""). Applying dropLast() to an empty sequence will result in an empty (sub-)sequence. This is what I would expect. How would you define a different result?
Remove last char from string/text in swift
var str1 = "123456789" str1.removeLast() print(str1) output:
12345678
