Pass variable from UIViewController to SwiftUI View - ios

Question

I can't find a way or a good tutorial to explain how to pass the value of a variable (String or Int) that is owned by a UIViewController to a SwiftUI view that is calling the view.
For example:
class ViewController: UIViewController {
var myString : String = "" // variable of interest
....
func methodThatChangeValueOfString(){
myString = someValue
}
}
// to make the view callable on SwiftUI
extension ViewController: UIViewControllerRepresentable {
typealias UIViewControllerType = ViewController
public func makeUIViewController(context: UIViewControllerRepresentableContext<ViewController>) -> ViewController {
return ViewController()
}
func updateUIViewController(_ uiViewController: ViewController, context: UIViewControllerRepresentableContext<ViewController>) {
}
}
In SwiftUI I'll have
struct ContentView: View {
var body: some View {
ViewController()
}
}
How can I take myString of the ViewController and use it in ContentView?
Thanks in advance

Answer 1

Use MVVM pattern it is what is recommended with SwiftUI.
Share a ViewModel between your SwiftUI View and your UIKit ViewController.
I suggest you start with the basic Apple SwiftUI tutorials. Specifically how to "Interface with UIKit"
https://developer.apple.com/tutorials/swiftui/interfacing-with-uikit
import SwiftUI
struct SwiftUIView: View {
#StateObject var sharedVM: SharedViewModel = SharedViewModel()
var body: some View {
VStack{
UIKitViewController_UI(sharedVM: sharedVM)
Text(sharedVM.myString)
}
}
}
class SharedViewModel: ObservableObject{
#Published var myString = "init String"
}
//Not an extension
struct UIKitViewController_UI: UIViewControllerRepresentable {
typealias UIViewControllerType = UIKitViewController
var sharedVM: SharedViewModel
func makeUIViewController(context: Context) -> UIKitViewController {
return UIKitViewController(vm: sharedVM)
}
func updateUIViewController(_ uiViewController: UIKitViewController, context: Context) {
}
}
class UIKitViewController: UIViewController {
let sharedVM: SharedViewModel
var runCount = 0
init(vm: SharedViewModel) {
self.sharedVM = vm
super.init(nibName: nil, bundle: nil)
//Sample update mimics the work of a Delegate or IBAction, etc
Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { timer in
self.runCount += 1
self.methodThatChangeValueOfString()
if self.runCount == 10 {
timer.invalidate()
}
}
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func methodThatChangeValueOfString(){
sharedVM.myString = "method change" + runCount.description
}
}
struct SwiftUIView_Previews: PreviewProvider {
static var previews: some View {
SwiftUIView()
}
}