AJIEKCX · July 18, 2023 17:25 · Jul 18, 2023
diff --git a/StackView.swift b/StackView.swift
@@ -0,0 +1,127 @@
+import Shared
+import SwiftUI
+
+/*
+ A custom implementation of the stack view wrapper with:
+ - no indices for `onBack` action
+ - no `getTitle`
+ - no `NavigationStack`
+ - custom UINavigationController
+
+ https://github.com/arkivanov/Decompose/blob/11a66f0ec46e42259af5510fc5bb28250e027924/sample/app-ios/app-ios/DecomposeHelpers/StackView.swift
+*/
+
+struct StackView<T: AnyObject, Content: View>: View {
+  @ObservedObject var stackValue: ObservableValue<ChildStack<AnyObject, T>>
+  var onBack: () -> Void
+  @ViewBuilder var childContent: (T) -> Content
+
+  var stack: [Child<AnyObject, T>] { stackValue.value.items }
+
+  var body: some View {
+    StackInteropView(
+      components: stack.map { $0.instance! },
+      onBack: onBack,
+      childContent: childContent
+    )
+    .ignoresSafeArea(.container)
+  }
+}
+
+private struct StackInteropView<T: AnyObject, Content: View>: UIViewControllerRepresentable {
+  var components: [T]
+  var onBack: () -> Void
+  var childContent: (T) -> Content
+
+  func makeCoordinator() -> Coordinator {
+    Coordinator(self)
+  }
+
+  func makeUIViewController(context: Context) -> UINavigationController {
+    context.coordinator.syncChanges(self)
+    let navigationController = CustomNavigationController(
+      rootViewController: context.coordinator.viewControllers.first!
+    )
+
+    return navigationController
+  }
+
+  func updateUIViewController(
+    _ navigationController: UINavigationController,
+    context: Context
+  ) {
+    context.coordinator.syncChanges(self)
+    navigationController.setViewControllers(
+      context.coordinator.viewControllers,
+      animated: true
+    )
+  }
+
+  private func createViewController(
+    _ component: T,
+    _ coordinator: Coordinator
+  ) -> NavigationItemHostingController {
+    let controller = NavigationItemHostingController(
+      rootView: childContent(component)
+    )
+    controller.coordinator = coordinator
+    controller.component = component
+    controller.onBack = onBack
+
+    return controller
+  }
+
+  private final class CustomNavigationController: UINavigationController, UIGestureRecognizerDelegate {
+    override func viewDidLoad() {
+      super.viewDidLoad()
+      navigationBar.isHidden = true
+      interactivePopGestureRecognizer?.delegate = self
+    }
+
+    // fixes swipes back, when parent stack view intercepts child's gestures
+    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
+      viewControllers.count > 1
+    }
+  }
+
+  fileprivate final class Coordinator: NSObject {
+    var parent: StackInteropView<T, Content>
+    var viewControllers = [NavigationItemHostingController]()
+    var preservedComponents = [T]()
+
+    init(_ parent: StackInteropView<T, Content>) {
+      self.parent = parent
+    }
+
+    func syncChanges(_ parent: StackInteropView<T, Content>) {
+      self.parent = parent
+      let count = max(preservedComponents.count, parent.components.count)
+
+      for i in 0..<count {
+        if (i >= parent.components.count) {
+          viewControllers.removeLast()
+        } else if (i >= preservedComponents.count) {
+          viewControllers.append(parent.createViewController(parent.components[i], self))
+        } else if (parent.components[i] !== preservedComponents[i]) {
+          viewControllers[i] = parent.createViewController(parent.components[i], self)
+        }
+      }
+
+      preservedComponents = parent.components
+    }
+  }
+
+  fileprivate final class NavigationItemHostingController: UIHostingController<Content> {
+    fileprivate(set) weak var coordinator: Coordinator?
+    fileprivate(set) var component: T?
+    fileprivate(set) var onBack: (() -> Void)?
+
+    override func viewDidDisappear(_ animated: Bool) {
+      super.viewDidDisappear(animated)
+
+      if isMovingFromParent && coordinator?.preservedComponents.last === component {
+        onBack?()
+      }
+    }
+  }
+}
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