How to resolve "AttributeGraph: cycle" warnings in the following code? - swift

Question

For context, the goal of the code below is to intercept a particular type of link inside a webview and handle navigation across a tabview natively (to a separate webview displaying the desired page) rather let the webview navigate itself. However, when I attempt to change the currentSelection to the desired index, I get a long list of "===AttributeGraph: cycle...===" messages. Below is the entirety of the code needed to repro this behavior:
import SwiftUI
import WebKit
#main
struct AttributeGraphCycleProofApp: App {
var body: some Scene {
WindowGroup {
ContentView(theController: Controller())
}
}
}
struct ContentView: View {
#StateObject var theController: Controller
#State var currentSelection = 0
private let selectedBackgroundColor = Color.green
var body: some View {
VStack(spacing: 12.0) {
HStack(spacing: .zero) {
ForEach(Array(0..<theController.viewModel.menuEntries.count), id: \.self) { i in
let currentMenuEntry = theController.viewModel.menuEntries[i]
Text(currentMenuEntry.title)
.padding()
.background(i == currentSelection ? selectedBackgroundColor : .black)
.foregroundColor(i == currentSelection ? .black : .gray)
}
}
TabView(selection: $currentSelection) {
let menuEntries = theController.viewModel.menuEntries
ForEach(Array(0..<menuEntries.count), id: \.self) { i in
let currentMenuEntry = theController.viewModel.menuEntries[i]
WrappedWebView(slug: currentMenuEntry.slug, url: currentMenuEntry.url) { destinationIndex in
// cycle warnings are logged when this line is executed
currentSelection = destinationIndex
}
}
}
.tabViewStyle(.page(indexDisplayMode: .never))
}
.padding()
.background(.black)
.onAppear { theController.start() }
}
}
class Controller: ObservableObject {
#Published var viewModel: ViewModel = ViewModel(menuEntries: [])
func start() {
// Represents network request to create dynamic menu entries
DispatchQueue.main.asyncAfter(deadline: .now().advanced(by: DispatchTimeInterval.seconds(1)), execute: { [weak self] in
self?.viewModel = ViewModel.create()
})
}
}
struct ViewModel {
let menuEntries: [MenuEntry]
static func create() -> Self {
return Self(menuEntries: [
MenuEntry(title: "Domain", slug: "domain", url: "https://www.example.com/"),
MenuEntry(title: "Iana", slug: "iana", url: "https://www.iana.org/domains/reserved"),
])
}
}
struct MenuEntry {
let title: String
let slug: String
let url: String
}
struct WrappedWebView: UIViewRepresentable {
var slug: String
var url: String
var navigateToSlug: ((Int) -> Void)? = nil
func makeCoordinator() -> WrappedWebView.Coordinator { Coordinator(self) }
func makeUIView(context: Context) -> WKWebView {
let webView = WKWebView()
webView.navigationDelegate = context.coordinator
return webView
}
func updateUIView(_ webView: WKWebView, context: Context) {
webView.isOpaque = false
if let wrappedUrl = URL(string: url), webView.url != wrappedUrl {
let request = URLRequest(url: wrappedUrl)
webView.load(request)
}
}
class Coordinator: NSObject, WKNavigationDelegate {
let parent: WrappedWebView
init(_ parent: WrappedWebView) {
self.parent = parent
}
func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction) async -> WKNavigationActionPolicy {
let url = navigationAction.request.url
if url?.absoluteString == parent.url {
return .allow
}
DispatchQueue.main.async { [weak self] in
guard let self = self else { return }
self.parent.navigateToSlug?(1)
}
return .cancel
}
}
}
All instrumentation and memory graph debugging are failing me as they don't describe the moment the leak occurs, all I know is that the critical line causing the leaks is the assignment of navigationIndex to currentSelection.