UIScrollView wrapped for SwiftUI, with support for pull to refresh using the refreshable modifier

ScrollViewWrapper.swift

//
//  ScrollViewWrapper.swift
//
//  Created by Mathijs Bernson on 10/03/2022.
//  Copyright © 2022 Q42. All rights reserved.
//

import SwiftUI
import UIKit

struct ScrollViewWrapper<Content: View>: View {
  @ViewBuilder let content: Content

  var body: some View {
    GeometryReader { proxy in
      ScrollViewControllerRepresentable(refreshControl: UIRefreshControl()) {
        content
          .frame(width: proxy.size.width)
      }
      .ignoresSafeArea()
    }
  }
}

private struct ScrollViewControllerRepresentable<Content: View>: UIViewControllerRepresentable {
  let refreshControl: UIRefreshControl
  @ViewBuilder let content: Content
  @Environment(\.refresh) private var action
  @State var isRefreshing: Bool = false

  func makeUIViewController(context: Context) -> ScrollViewController<Content> {
    let viewController = ScrollViewController(
      refreshControl: refreshControl,
      view: content
    )
    viewController.onRefresh = {
      refresh()
    }
    return viewController
  }

  func updateUIViewController(_ viewController: ScrollViewController<Content>, context: Context) {
    if isRefreshing {
      viewController.refreshControl.beginRefreshing()
    } else {
      viewController.refreshControl.endRefreshing()
    }
    viewController.hostingController.rootView = content
  }

  func refresh() {
    Task {
      isRefreshing = true
      await action?()
      isRefreshing = false
    }
  }
}

private class ScrollViewController<Content: View>: UIViewController, UIScrollViewDelegate {
  let scrollView = UIScrollView()
  let refreshControl: UIRefreshControl
  let hostingController: UIHostingController<Content>

  var onRefresh: (() -> Void)?

  init(refreshControl: UIRefreshControl, view: Content) {
    self.refreshControl = refreshControl
    self.hostingController = UIHostingController(rootView: view)
    super.init(nibName: nil, bundle: nil)
  }

  required init?(coder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

  override func loadView() {
    view = scrollView
  }

  override func viewDidLoad() {
    super.viewDidLoad()

    refreshControl.addTarget(self, action: #selector(didPullToRefresh), for: .valueChanged)

    scrollView.refreshControl = refreshControl
    scrollView.delegate = self

    hostingController.willMove(toParent: self)
    scrollView.addSubview(hostingController.view)
    hostingController.view.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
      hostingController.view.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor),
      hostingController.view.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor),
      hostingController.view.topAnchor.constraint(equalTo: scrollView.topAnchor),
      hostingController.view.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor),
    ])

    hostingController.didMove(toParent: self)
    hostingController.view.backgroundColor = .clear
  }

  override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
    super.traitCollectionDidChange(previousTraitCollection)

    hostingController.view.invalidateIntrinsicContentSize()
  }

  @objc func didPullToRefresh(_ sender: UIRefreshControl) {
    onRefresh?()
  }
}