How to use traitCollectionDidChange method of CollectionViewController class

...19				as? CollectionViewLayout else { return }20		collectionViewLayout.delegate = self21  }22	23	override func traitCollectionDidChange(24		_ previousTraitCollection: UITraitCollection?25	) {26		super.traitCollectionDidChange(previousTraitCollection)27		guard previousTraitCollection?.preferredContentSizeCategory28			!= traitCollection.preferredContentSizeCategory29			else { return }30		collectionView.collectionViewLayout.invalidateLayout()31	}32  // MARK: - Actions33  @IBAction func cancelBarButtonDidTouchUpInside(_ sender: UIBarButtonItem) {34    DispatchQueue.main.async { [weak self] in35      self?.dismiss(animated: true)36    }37  }38}39// MARK: - UICollectionViewDataSource40extension CollectionViewController {...

...13  public var viewWillAppear = false14  public var viewWillDisappear = false15  public var viewDidAppear = false16  public var viewDidDisappear = false17  public var traitCollectionDidChange = false18  public init(navigator: Navigator? = nil) {19    let layout = ListViewLayout(stickyHeaders: false, topContentInset: 0, stretchToEdge: false)20    let collectionVC = CollectionViewController(layout: layout)21    collectionVC.backgroundImage = UIImage()22    let listController = LegacyListController()23    let navigator = navigator ?? BasicNavigator(parent: nil)24    let presenter = FakePresenter()25    super26      .init(27        navigator: navigator,28        viewController: collectionVC,29        presenter: presenter,30        listController: listController31      )32    viewController.events33      .subscribe(onNext: { [weak self] event in34        self?.handle(event)35      })36      .disposed(by: disposeBag)37    collectionVC.view.frame = CGRect(x: 0, y: 0, width: 500, height: 10_000)38  }39  // MARK: - ListControllerSizeDelegate40  override public func listController(41    _ listController: ListController,42    sizeFor model: ListCellModel,43    at indexPath: IndexPath,44    constrainedTo sizeConstraints: ListSizeConstraints45  ) -> CGSize? {46    CGSize(width: sizeConstraints.adjustedContainerSize.width, height: 24)47  }48  private func handle(_ event: ListViewControllerEvent) {49    switch event {50    case .traitCollectionDidChange:51      traitCollectionDidChange = true52    case .viewDidDisappear:53      viewDidDisappear = true54    case .viewDidLoad:55      viewDidLoad = true56    case .viewWillAppear:57      viewWillAppear = true58    case .viewWillDisappear:59      viewWillDisappear = true60    case .viewDidAppear:61      viewDidAppear = true62    }63  }64}...

...15  public var viewWillAppear = false16  public var viewWillDisappear = false17  public var viewDidAppear = false18  public var viewDidDisappear = false19  public var traitCollectionDidChange = false20  public init(navigator: Navigator? = nil) {21    let layout = ListViewLayout(stickyHeaders: false, topContentInset: 0, stretchToEdge: false)22    let collectionVC = CollectionViewController(layout: layout)23    collectionVC.backgroundImage = UIImage()24    let listController = LegacyListController()25    let presenter = FakePresenter()26    super27      .init(28        parentNavigator: navigator,29        collectionViewController: collectionVC,30        presenter: presenter,31        listController: listController32      )33    viewController.events34      .subscribe(onNext: { [weak self] event in35        self?.handle(event)36      })37      .disposed(by: disposeBag)38    collectionVC.view.frame = CGRect(x: 0, y: 0, width: 500, height: 10_000)39  }40  // MARK: - ListControllerSizeDelegate41  override public func listController(42    _ listController: ListController,43    sizeFor model: ListCellModel,44    at indexPath: IndexPath,45    constrainedTo sizeConstraints: ListSizeConstraints46  ) -> CGSize? {47    CGSize(width: sizeConstraints.adjustedContainerSize.width, height: 24)48  }49  private func handle(_ event: ListViewControllerEvent) {50    switch event {51    case .traitCollectionDidChange:52      traitCollectionDidChange = true53    case .viewDidDisappear:54      viewDidDisappear = true55    case .viewDidLoad:56      viewDidLoad = true57    case .viewWillAppear:58      viewWillAppear = true59    case .viewWillDisappear:60      viewWillDisappear = true61    case .viewDidAppear:62      viewDidAppear = true63    }64  }65}...

1import UIKit2class ViewController: UIViewController {3    override func viewDidLoad() {4        super.viewDidLoad()5    }6    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {7        super.traitCollectionDidChange(previousTraitCollection)8        if traitCollection.hasDifferentColorAppearance(comparedTo: previousTraitCollection) {9        }10    }

1import UIKit2class ViewController: UICollectionViewController {3    override func viewDidLoad() {4        super.viewDidLoad()5    }6    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {7        super.traitCollectionDidChange(previousTraitCollection)8        print("traitCollectionDidChange")9    }10    override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {11        print("willTransition")12    }13    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {14        print("viewWillTransition")15    }16    override func viewWillLayoutSubviews() {17        print("viewWillLayoutSubviews")18    }19    override func viewDidLayoutSubviews() {20        print("viewDidLayoutSubviews")21    }22    override func viewDidAppear(_ animated: Bool) {23        print("viewDidAppear")24    }25    override func viewWillDisappear(_ animated: Bool) {26        print("viewWillDisappear")27    }28    override func viewDidDisappear(_ animated: Bool) {29        print("viewDidDisappear")30    }31    override func viewDidUnload() {32        print("viewDidUnload")33    }34    override func didReceiveMemoryWarning() {35        print("didReceiveMemoryWarning")36    }37}

1import UIKit2class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {3    override func viewDidLoad() {4        super.viewDidLoad()5    }6    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {7        super.viewWillTransition(to: size, with: coordinator)8        collectionView.collectionViewLayout.invalidateLayout()9    }10    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {11        super.traitCollectionDidChange(previousTraitCollection)12        collectionView.collectionViewLayout.invalidateLayout()13    }14    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {15    }16    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {17        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)18    }19}20import UIKit21class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {22    override func viewDidLoad() {23        super.viewDidLoad()24    }25    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {26        super.viewWillTransition(to: size, with: coordinator)27        collectionView.collectionViewLayout.invalidateLayout()28    }29    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {30        super.traitCollectionDidChange(previousTraitCollection)31        collectionView.collectionViewLayout.invalidateLayout()32    }33    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {34    }35    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {36        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)37    }38    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {39        if traitCollection.horizontalSizeClass == .compact {40            return CGSize(width: collectionView.frame.width, height: 100)41        } else {42            return CGSize(width: collectionView.frame.width/2, height: 100)43        }44    }45}

1import UIKit2class ViewController: UIViewController {3    override func viewDidLoad() {4        super.viewDidLoad()5    }6    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {7        print("traitCollectionDidChange")8    }9    override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {10        print("willTransition")11    }12    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {13        print("viewWillTransition")14    }15}16extension ViewController: UICollectionViewDelegateFlowLayout {17    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {18        print("traitCollectionDidChange")19    }20    override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {21        print("willTransition")22    }23    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {24        print("viewWillTransition")25    }26}

1import UIKit2class ViewController: UIViewController {3    override func viewDidLoad() {4        super.viewDidLoad()5    }6    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {7        if self.traitCollection.horizontalSizeClass == .compact {8        }9        else {10        }11    }12    override func didReceiveMemoryWarning() {13        super.didReceiveMemoryWarning()14    }15}16import UIKit17class ViewController: UIViewController {18    override func viewDidLoad() {19        super.viewDidLoad()20    }21    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {22        if self.traitCollection.horizontalSizeClass == .compact {23        }24        else {25        }26    }27    override func didReceiveMemoryWarning() {28        super.didReceiveMemoryWarning()29    }30}31import UIKit32class ViewController: UIViewController {33    override func viewDidLoad() {34        super.viewDidLoad()35    }36    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {37        if self.traitCollection.horizontalSizeClass == .compact {38        }39        else {40        }41    }42    override func didReceiveMemoryWarning() {43        super.didReceiveMemoryWarning()44    }45}

1import UIKit2class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {3    override func viewDidLoad() {4        super.viewDidLoad()5    }6    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {7        print("viewWillTransition")8        self.collectionView.collectionViewLayout.invalidateLayout()9    }10    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {11    }12    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {13        let cell:CollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as! CollectionViewCell14    }15    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {16        print("You selected cell #\(indexPath.item)!")17    }18}19extension ViewController: UICollectionViewDelegateFlowLayout {20    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {21        return CGSize(width: width, height: height)22    }23    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {24    }25    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {26    }27    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {28    }29}

1import UIKit2class ViewController: UICollectionViewController {3    var cellSize: CGSize {4        guard let flowLayout = collectionView?.collectionViewLayout as? UICollectionViewFlowLayout else { return CGSize.zero }5        let width = (collectionView!.bounds.width - flowLayout.sectionInset.left - flowLayout.sectionInset.right - flowLayout.minimumInteritemSpacing) / 26        return CGSize(width: width, height: width)7    }8    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {9        super.traitCollectionDidChange(previousTraitCollection)10        collectionView?.collectionViewLayout.invalidateLayout()11    }12    override func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {13    }14}

1import UIKit2class ViewController: UICollectionViewController {3    var cellSize: CGSize {4        guard let flowLayout = collectionView?.collectionViewLayout as? UICollectionViewFlowLayout else { return CGSize.zero }5        let width = (collectionView!.bounds.width - flowLayout.sectionInset.left - flowLayout.sectionInset.right - flowLayout.minimumInteritemSpacing) / 26        return CGSize(width: width, height: width)7    }8    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {9        super.traitCollectionDidChange(previousTraitCollection)10        collectionView?.collectionViewLayout.invalidateLayout()11    }12    override func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {13    }14}Kit15class ViewController: UIViewController {16    override func viewDidLoad() {17        super.viewDidLoad()18    }19    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {20        if self.traitCollection.horizontalSizeClass == .compact {21        }22        else {23        }24    }25    override func didReceiveMemoryWarning() {26        super.didReceiveMemoryWarning()27    }28}29import UIKit30class ViewController: UIViewController {31    override func viewDidLoad() {32        super.viewDidLoad()33    }34    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {35        if self.traitCollection.horizontalSizeClass == .compact {36        }37        else {38        }39    }40    override func didReceiveMemoryWarning() {41        super.didReceiveMemoryWarning()42    }43}44import UIKit45class ViewController: UIViewController {46    override func viewDidLoad() {47        super.viewDidLoad()48    }49    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {50        if self.traitCollection.horizontalSizeClass == .compact {51        }52        else {53        }54    }55    override func didReceiveMemoryWarning() {56        super.didReceiveMemoryWarning()57    }58}

1import UIKit2class ViewController: UICollectionViewController {3    var cellSize: CGSize {4        guard let flowLayout = collectionView?.collectionViewLayout as? UICollectionViewFlowLayout else { return CGSize.zero }5        let width = (collectionView!.bounds.width - flowLayout.sectionInset.left - flowLayout.sectionInset.right - flowLayout.minimumInteritemSpacing) / 26        return CGSize(width: width, height: width)7    }8    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {9        super.traitCollectionDidChange(previousTraitCollection)10        collectionView?.collectionViewLayout.invalidateLayout()11    }12    override func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {13    }14}