Use existing pages instead of initialised controllers in PageViewController - swift

Question

I'm using a PageViewController from this tutorial
Since the pages are being added as controllers, here:
controllers = parent.pages.map { UIHostingController(rootView: $0) }
Whenever they're updated in my SwiftUI view, the user can't see any updates, since (i'm guessing) the init method doesn't refresh.
So how am I able to use the current pages instead of instantiating a controllers array?
Here is my code:
PageViewController.swift
import SwiftUI
import UIKit
struct PageViewController<Page: View>: UIViewControllerRepresentable {
var pages: [Page]
var onLast: () -> AnyView
#Binding var currentPage: Int
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
func makeUIViewController(context: Context) -> UIPageViewController {
let pageViewController = UIPageViewController(
transitionStyle: .scroll,
navigationOrientation: .vertical)
pageViewController.dataSource = context.coordinator
pageViewController.delegate = context.coordinator
return pageViewController
}
func updateUIViewController(_ pageViewController: UIPageViewController, context: Context) {
pageViewController.setViewControllers(
[context.coordinator.controllers[currentPage]], direction: .forward, animated: true)
}
class Coordinator: NSObject, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
var parent: PageViewController
var controllers = [UIViewController]()
init(_ pageViewController: PageViewController) {
parent = pageViewController
controllers = parent.pages.map { UIHostingController(rootView: $0) }
}
func pageViewController(
_ pageViewController: UIPageViewController,
viewControllerBefore viewController: UIViewController) -> UIViewController?
{
guard let index = controllers.firstIndex(of: viewController) else {
return nil
}
if index == 0 {
return controllers.last
}
return controllers[index - 1]
}
func pageViewController(
_ pageViewController: UIPageViewController,
viewControllerAfter viewController: UIViewController) -> UIViewController?
{
guard let index = controllers.firstIndex(of: viewController) else {
return nil
}
if index + 1 == controllers.count {
return controllers.first
}
return controllers[index + 1]
}
func pageViewController(
_ pageViewController: UIPageViewController,
didFinishAnimating finished: Bool,
previousViewControllers: [UIViewController],
transitionCompleted completed: Bool) {
if completed,
let visibleViewController = pageViewController.viewControllers?.first,
let index = controllers.firstIndex(of: visibleViewController) {
if index + 1 == controllers.count {
print("index: \(index)")
print(controllers.count)
controllers.append(UIHostingController(rootView: parent.onLast()))
}
parent.currentPage = index
}
}
}
}
struct PageView<Page: View>: View, Equatable {
static func == (lhs: PageView<Page>, rhs: PageView<Page>) -> Bool {
return true
}
var pages: [Page]
var onLast: () -> AnyView
#Binding var currentPage: Int
var body: some View {
PageViewController(pages: pages, onLast: onLast, currentPage: $currentPage)
}
}
SwiftUI View
import SwiftUI
struct Test: View {
#State var color: Color = Color.blue
var body: some View {
PageView(
pages: [
AnyView(
color
),
AnyView(
Color.purple
),
AnyView(Color.green),
AnyView(Color.orange),
],
onLast: {
color = Color.red
},
currentPage: $currentPage
)
.equatable()
}
}

Answer 1

Well, UIKit views should live in own world, SwiftUI views in own. Actually it is expected here that parent state will not update something deep inside bridged UIKit, even if it looks like it is in same stack, but actually it is just a function and it is called god-damn-known-when.
Anyway the approach is to solve it is simple - use SwiftUI tools to update SwiftUI views. Here it looks appropriate to use ObservableObject view model with explicit view observed it and work with that view model, because it is a reference-type.
Here is a sketch:
class ViewModel: ObservableObject {
#Published var color = Color.blue
}
struct Test: View {
#StateObject var vm = ViewModel() // << owner !!
var body: some View {
PageView(
pages: [
AnyView(
NativePath(vm: vm) // << inject
),
AnyView(
Color.purple
),
AnyView(Color.green),
AnyView(Color.orange),
],
onLast: {
vm.color = Color.red // << update by ref
},
currentPage: $currentPage
)
.equatable()
}
struct NativePath: View {
#ObservedObject var vm: ViewModel // << observe explicitly
var body: some View {
vm.color // << updated
}
}
}