UIPreview

이젠 Command + R 을 할 필요가 없다. https://developer.apple.com/documentation/xcode/previewing-your-apps-interface-in-xcode 참고

• view Controller

#if canImport(SwiftUI) && DEBUG
import SwiftUI
struct UIViewControllerPreview<ViewController: UIViewController>: UIViewControllerRepresentable {
    let viewController: ViewController

    init(_ builder: @escaping () -> ViewController) {
        viewController = builder()
    }

    // MARK: - UIViewControllerRepresentable
    func makeUIViewController(context: Context) -> ViewController {
        viewController
    }

    func updateUIViewController(_ uiViewController: ViewController, context: UIViewControllerRepresentableContext<UIViewControllerPreview<ViewController>>) {
        return
    }
}
#endif

#if canImport(SwiftUI) && DEBUG
import SwiftUI

let deviceNames: [String] = [
    "iPhone SE",
    "iPhone 11 Pro Max",
    "iPad Pro (11-inch)"
]

@available(iOS 13.0, *)
struct ViewController_Preview: PreviewProvider {
  static var previews: some View {
    ForEach(deviceNames, id: \.self) { deviceName in
      UIViewControllerPreview {
        ViewController()
      }.previewDevice(PreviewDevice(rawValue: deviceName))
        .previewDisplayName(deviceName)
    }
  }
}
#endif

// WWDC2023 

#Preview("ViewController"){
    ViewController()
}

//
#if DEBUG

import SwiftUI

struct ViewControllerRepresentable: UIViewControllerRepresentable {
    typealias UIViewControllerType = ViewController

    func makeUIViewController(context: Context) -> UIViewControllerType {
        ViewController(nibName: nil, bundle: nil)
    }
    
    func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {
        
    }
}

struct ViewController_Previews: PreviewProvider {
    static var previews: some View {
        ViewControllerRepresentable()
    }
}

#endif

• UIView

import Foundation
import UIKit

final class SimpleView: UIView {
    
    let label = UILabel()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        label.translatesAutoresizingMaskIntoConstraints = false
        label.text = "Simple Label"
        
        addSubview(label)
        
        NSLayoutConstraint.activate([
            label.centerXAnchor.constraint(equalTo: centerXAnchor),
            label.centerYAnchor.constraint(equalTo: centerYAnchor)
        ])
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override var intrinsicContentSize: CGSize {
        return CGSize(width: 200, height: 200)
    }
}

#if canImport(SwiftUI) && DEBUG
import SwiftUI

@available(iOS 13, *)
public struct UIViewPreview<View: UIView>: UIViewRepresentable {
    public let view: View

    public init(_ builder: @escaping () -> View) {
        view = builder()
    }

    // MARK: - UIViewRepresentable
    public func makeUIView(context: Context) -> UIView {
        return view
    }

    public func updateUIView(_ view: UIView, context: Context) {
        view.setContentHuggingPriority(.defaultHigh, for: .horizontal)
        view.setContentHuggingPriority(.defaultHigh, for: .vertical)
    }
}
#endif

#if canImport(SwiftUI) && DEBUG
import SwiftUI

@available(iOS 13.0, *)
struct SimpleView_Preview: PreviewProvider {
  static var previews: some View {
    UIViewPreview {
      let button = SimpleView()
      return button
    }.previewLayout(.sizeThatFits)
     .padding(10)
  }
}
#endif

해당내용은 주말에 정리를 해야겠다.