Using a UISegmentedControl like a UISwitch - swift

Question

Is it possible to use a UISegmentedControl with 3 segments as if it was a three-way UISwitch? I tried to use one as a currency selector in the settings section of my app with no luck, it keeps reseting to the first segment when I switch views and that creates a big mess.
I proceeded like that:
IBAction func currencySelection(_ sender: Any) {
switch segmentedControl.selectedSegmentIndex {
case 0:
WalletViewController.currencyUSD = true
WalletViewController.currencyEUR = false
WalletViewController.currencyGBP = false
MainViewController().refreshPrices()
print(0)
case 1:
WalletViewController.currencyUSD = false
WalletViewController.currencyEUR = true
WalletViewController.currencyGBP = false
MainViewController().refreshPrices()
print(1)
case 2:
WalletViewController.currencyUSD = false
WalletViewController.currencyEUR = false
WalletViewController.currencyGBP = true
MainViewController().refreshPrices()
print(2)
default:
break
}
}

Answer 1

The UISegmentedControl is implemented in the
SettingsViewController of the app to choose between currencies to
display in the MainViewController.
(Taken from a comment in #pacification's answer.)
This was the missing piece I was looking for. It provides a lot of context.
TL;DR;
Yes, you can use a three segment UISegmentedControl as a three-way switch. The only real requirement is that you can have only one value or state selected.
But I wasn't grasping why your code referred to two view controllers and some of switching views resulting in resetting the segment. One very good way to do what you want is to:
Have MainViewController present SettingsViewController. Presenting it modally means the user is only doing one thing at a time. When they are making setting changes, you do not want them adding new currency values.
Create a delegate protocol in SettingsViewController and make MainViewController conform to it. This tightly-couples changes made to the settings to the view controller interested in what those changes are.
Here's a template for what I'm talking about:
SettingsViewController:
protocol SettingsVCDelegate {
func currencyChanged(sender: SettingsViewController)
}
class SettingsViewController : UIViewController {
var delegate:SettingsVCDelegate! = nil
var currency:Int = 0
#IBAction func valueChanged(_ sender: UISegmentedControl) {
currency = sender.selectSegmentIndex
delegate.currencyChanged(sender:self)
}
}
MainViewController:
class MainViewController: UIViewController, SettingsVCDelegate {
var currency:Int = 0
let settingsVC = SettingsViewController()
override func viewDidLoad() {
super.viewDidLoad()
settingsVC.delegate = self
}
func presentSettings() {
present(settingsVC, animated: true, completion: nil)
}
func currencyChanged(sender:SettingsViewController) {
currency = sender.currency
}
}
You can also create an enum of type Int to make your code more readable, naming each value as currencyUSD, currencyEUR, and currencyGBP. I'll leave that to you as a learning exercise.

Answer 2

it keeps reseting to the first segment when I switch views
yes, it is. to avoid this situation you should set the correct switch value to the segmentedControl.selectedSegmentIndex every time when you load your view with UISegmentedControl.
UPD
Ok, the behavior of MainViewController can be similar to this:
final class MainViewController: UIViewController {
private var savedValue = 0
override func viewDidLoad() {
super.viewDidLoad()
}
func openSettingsController() {
let viewController = SettingsController.instantiate() // simplify code a bit. use the full controller initialization
viewController.configure(value: savedValue, onValueChanged: { [unowned self] value in
self.savedValue = value
})
navigationController?.pushViewController(viewController, animated: true)
}
}
And the SettingsViewController:
final class SettingsViewController: UIViewController {
#IBOutlet weak var segmentedControl: UISegmentedControl!
private var value: Int = 0
var onValueChanged: ((Int) -> Void)?
func configure(value: Int, onValueChanged: #escaping ((Int) -> Void)) {
self.value = value
self.onValueChanged = onValueChanged
}
override func viewDidLoad() {
super.viewDidLoad()
segmentedControl.selectedSegmentIndex = value
}
#IBAction func valueChanged(_ sender: UISegmentedControl) {
onValueChanged?(sender.selectedSegmentIndex)
}
}
The main idea that you should keep your selected value if you moving from SettingsViewController. For this thing you can create closure
var onValueChanged: ((Int) -> Void)?
that pass back to MainViewController the selected UISegmentedControl value. And in future when you will open the SettingsViewController again you just configure() this value and set it to UI.