Use Xcode 11 UI Preview feature for UIKit Views

XcodePreviews_UIKit.swift

import SwiftUI

final class SomeView: UIView {
    init() {
        super.init(frame: CGRect.zero)
        // TODO: create your view content
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

final class SomeViewController: UIViewController {
    let someView = SomeView()

    override func viewDidLoad() {
        super.viewDidLoad()
        setup()
    }

    func setup() {
        someView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(someView)

        // TODO: adapt to your needs
        someView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        someView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
        someView.widthAnchor.constraint(equalToConstant: 400.0).isActive = true
        someView.heightAnchor.constraint(equalToConstant: 100.0).isActive = true
    }
}

extension SomeViewController: UIViewControllerRepresentable {
    typealias UIViewControllerType = SomeViewController

    @available(iOS 13.0, *)
    func makeUIViewController(context: UIViewControllerRepresentableContext<UIViewControllerType>) -> UIViewControllerType {
        return SomeViewController()
    }

    @available(iOS 13.0, *)
    func updateUIViewController(_ uiViewController: UIViewControllerType, context: UIViewControllerRepresentableContext<UIViewControllerType>) {}
}

@available(iOS 13, *)
struct SomeViewController_Previews: PreviewProvider {
    static var previews: some View {
        SomeViewController()
    }
}