Swift: How to access a Switch Statement in a Swift file (error: Statements are not allowed at the top level)?

Question

I am still new to Swift and coding in general and I am trying to create some kind of option for the user to change colored themes.

But I am clueless on how to access a switch statement in a swift file (or how to encapsulate it) and how to access the set variable?

So far I let the user choose a theme in a settings view controller and the name of the theme is saved in UserDefaults in the key "theme".

In a file called themes.swift I have created a switch statement to check for the names. Each case can obviously set a couple of variables I have declared above the switch statement.

But I get the error that "Statements are not allowed at the top level"?

How can I fix this? And what can I do to let the switch statement run each time a view controller is presented to check for the correct colors or let it run once a new theme is selected and set the variables? I understand the error message but I have no idea on how to fix this.

For instance this is how I have set up the themes.swift file so far:

import UIKit

var theme = UserDefaults.standard.string(forKey: "themes")

var background: UIColor?
var labelColor: UIColor?
var buttonColor: UIColor?


switch theme {
    case "Red":
        background = UIColor(named: "darkRed")
        labelColor = UIColor(named: "labelRed")
        buttonColor = UIColor(named: "buttonRed")
    case "Blue":
        background = UIColor(named: "darkBlue")
        labelColor = UIColor(named: "labelBlue")
        buttonColor = UIColor(named: "buttonBlue")
    default:
        return
}

So how can I access those variables?

Besides the top level error, can I just access the variables like I would normally do because they are global variables?

Eg. startButton.setTitleColor(buttonColor, for: .normal) ?

Answer 1

You are getting this error because you have your switch statement just sitting inside some class or struct (it's not clear where you have this code implemented). To fix your error you will need to put that switch inside a function. Perhaps you could create a function called setTheme, like so:

var theme = UserDefaults.standard.string(forKey: "themes")

var background: UIColor?
var labelColor: UIColor?
var buttonColor: UIColor?

func setTheme() {
  //First, check to make sure theme is not nil
  guard let theme = self.theme else { return }
  switch theme {
  case "Red":
    background = UIColor(named: "darkRed")
    labelColor = UIColor(named: "labelRed")
    buttonColor = UIColor(named: "buttonRed")
  case "Blue":
    background = UIColor(named: "darkBlue")
    labelColor = UIColor(named: "labelBlue")
    buttonColor = UIColor(named: "buttonBlue")
  default:
    return
  }
}

Another option would be to make your UIColor? attributes computed variables. For example:

var background: UIColor? {
  guard let theme = self.theme else { return nil }
  switch theme {
    case "Red": return UIColor(named: "darkRed")
    case "Blue": return UIColor(named: "darkBlue")
    default: return nil
  }
}