SwiftUI previews for UIKit

CustomVC.swift

import UIKit

final class CustomVC: UIViewController {
    
    private lazy var contentView: CustomView = CustomView()
    
    // MARK: - Life cycle
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    override var preferredStatusBarStyle: UIStatusBarStyle {
        return .default
    }
    
    override func loadView() {
        view = contentView
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setup()
    }

    // MARK: - Private functions
    private func setup() {
    
    }
  
}

#if DEBUG
#if targetEnvironment(simulator)
import SwiftUI

@available(iOS 13.0, *)
struct CustomVC_Previews: PreviewProvider {
    
    static var devices = AppConstants.previewDevices // ["iPhone SE (1st generation)", "iPhone 8 (14.3)", "iPhone 12", "iPhone 12 Pro Max"]
    
    static var platform: PreviewPlatform? {
        return SwiftUI.PreviewPlatform.iOS
    }
    
    static var previews: some SwiftUI.View {
        ForEach(devices, id: \.self) { deviceName in
            Group {
                UIViewControllerPreview {
                    MainVC()
                }
            }.previewDevice(PreviewDevice(rawValue: deviceName))
            .previewDisplayName(deviceName)
        }
        
    }
}
#endif
#endif

CustomView.swift

final class CustomView: UIView {
  
    // MARK: - Life cycle
    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }
  
    // MARK: - Private functions
    private func setup() {
        
        setupLayout()
    }
  
    private func setupLayout() {
        
        layer.cornerRadius = 8.0
        clipsToBounds = true
        layer.borderWidth = 1.0
        layer.borderColor = UIColor.black.cgColor
    }

}

#if DEBUG
#if targetEnvironment(simulator)
import SwiftUI
@available(iOS 13.0, *)
struct CustomViewn_Previews: PreviewProvider {
    
    static var devices = AppConstants.previewDevices // ["iPhone SE (1st generation)", "iPhone 8 (14.3)", "iPhone 12", "iPhone 12 Pro Max"]
    
    static var platform: PreviewPlatform? {
        return SwiftUI.PreviewPlatform.iOS
    }
    
    static var previews: some SwiftUI.View {
        ForEach(devices, id: \.self) { deviceName in
            Group {
                UIViewPreview {
                    CustomView(frame: CGRect.zero)
                    
                }.frame(minWidth: 100, maxWidth: 200, minHeight: 50, maxHeight: 50)
            }.previewDevice(PreviewDevice(rawValue: deviceName))
            .previewDisplayName(deviceName)
        }
        
    }
}
#endif
#endif

Podfile.rb

// Inspired by CocoaHeads Ukraine 2020 Session - https://www.youtube.com/watch?v=V03NMBjumjA
// Aware of static libs at Cocoapods - installer fix below

post_install do |installer|
    
    installer.pods_project.targets.each do |target|
      
      target.build_configurations.each do |config|
        
        config.build_settings['ENABLE_BITCODE'] = 'NO'
        config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = deployment_target
        config.build_settings['MATCH_O_TYPE'] = 'staticlib'
        config.build_settings['MATCH_O_TYPE[sdk=iphonesimulator*]'] = 'mh_dylib'
        
        if config.name == 'Debug'
          config.build_settings['OTHER_SWIFT_FLAGS'] = ['$(inherited)', '-Onone']
          config.build_settings['SWIFT_OPTIMIZATION_LEVEL'] = '-Owholemodule'
        end
        
      end
      
    end
    
    installer.generated_projects.each do |project|
      project.build_configurations.each do |bc|
        bc.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = deployment_target
      end
    end
    
  end

UIViewControllerPreview.swift

import SwiftUI
import UIKit

@available(iOS 13.0, *)
struct UIViewControllerPreview: SwiftUI.View {
    
    private let factory: () -> UIViewController
    
    init(factory: @escaping () -> UIViewController) {
        self.factory = factory
    }
    
    var body: some SwiftUI.View {
        Renderer(factory)
    }
    
    private struct Renderer: UIViewControllerRepresentable {
        
        private let factory: () -> UIViewController
        
        init(_ factory: @escaping () -> UIViewController) {
            self.factory = factory
        }
        
        func makeUIViewController(context: Context) -> UIViewController {
            return factory()
        }
        
        func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {
            
        }
        
    }
   
}

UIViewPreview.swift

import SwiftUI
import UIKit

@available(iOS 13.0, *)
struct UIViewPreview: SwiftUI.View {
    
    private let factory: () -> UIView
    
    init(factory: @escaping () -> UIView) {
        self.factory = factory
    }
    
    var body: some SwiftUI.View {
        Renderer(factory)
    }
    
    private struct Renderer: UIViewRepresentable {
        
        private let factory: () -> UIView
        
        init(_ factory: @escaping () -> UIView) {
            self.factory = factory
        }
        
        func makeUIView(context: Context) -> UIView {
            return factory()
        }
        
        func updateUIView(_ uiView: UIView, context: Context) {
            
        }
        
    }
   
}