UIHostingController: SwiftUI dentro de UIKit

¿Qué es UIHostingController?

import SwiftUI
let swiftUIView = Text("Hello from SwiftUI")
let hostingVC = UIHostingController(rootView: swiftUIView)

Integración en un UIViewController

class MyViewController: UIViewController {
  override func viewDidLoad() {
    super.viewDidLoad()
    let child = UIHostingController(rootView: ContentView())
    addChild(child)
    view.addSubview(child.view)
    child.view.frame = view.bounds
    child.didMove(toParent: self)
  }
}

Auto Layout con un controlador de hosting

child.view.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
  child.view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
  child.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
  child.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
  child.view.bottomAnchor.constraint(equalTo: view.bottomAnchor)
])

Actualización de la vista raíz

let hostingVC = UIHostingController(rootView: MyView(count: 0))
// Later:
hostingVC.rootView = MyView(count: 5)

Presentación modal

let vc = UIHostingController(rootView: MySwiftUIView())
present(vc, animated: true)

Inserción en la pila de navegación

let vc = UIHostingController(rootView: DetailView())
navigationController?.pushViewController(vc, animated: true)

Uso compartido de datos mediante ObservableObject

let model = SharedModel()
let vc = UIHostingController(rootView: SwiftUIView().environmentObject(model))
// Changes to model in UIKit update SwiftUI and vice versa

Cálculo del tamaño del controlador de hosting

let size = hostingVC.sizeThatFits(in: CGSize(width: 320, height: UIView.layoutFittingCompressedSize.height))
hostingVC.view.frame.size = size

Apariencia y estilo

hostingVC.overrideUserInterfaceStyle = .dark

Configuración de una app basada en escenas

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options: UIScene.ConnectionOptions) {
  guard let windowScene = scene as? UIWindowScene else { return }
  let window = UIWindow(windowScene: windowScene)
  window.rootViewController = UIHostingController(rootView: ContentView())
  self.window = window
  window.makeKeyAndVisible()
}

Casos de uso

// UIKit app gradually migrated:
// - Old screens: UIViewController
// - New screens: UIHostingController(rootView: NewFeatureView())

Comprobación rápida

Repaso de la lección