Creates a UIViewController with Blurred Background Which acts like a UIHostingController for SwiftUI Views (Useful for UIKit developers using SwiftUI Views for Modal Views)

BlurredHostingController.swift

//
//  BluredBackgroundHostingController.swift
//  v1.0.1
//
//  Created by Ashley Chapman on 07/04/2020.
//  Copyright © 2020 Ashley Chapman. All rights reserved.
//

import UIKit

class BlurredHostingController: UIViewController {

    // Variables
    var hostingController: UIViewController!
    var blurEffect: UIBlurEffect.Style = .prominent
    var translucentEffect: TranslucentEffect = .regular
    
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        self.view.backgroundColor = nil
        
        if (translucentEffect != .opaque) {
            let blurEffect = UIBlurEffect(style: self.blurEffect)
            let blurEffectView = UIVisualEffectView(effect: blurEffect)
            blurEffectView.frame = self.view.frame
            
            self.view.addSubview(blurEffectView)
            
            NSLayoutConstraint.activate([
                blurEffectView.widthAnchor.constraint(equalTo: view.widthAnchor),
                blurEffectView.heightAnchor.constraint(equalTo: view.heightAnchor),
                blurEffectView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
                blurEffectView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
            ])
        }
        
        self.addChild(hostingController)
        hostingController.view.translatesAutoresizingMaskIntoConstraints = false
        hostingController.view.alpha = translucent()
        hostingController.view.backgroundColor = nil
        
        self.view.addSubview(hostingController.view)
        hostingController.didMove(toParent: self)
        
        NSLayoutConstraint.activate([
            hostingController.view.widthAnchor.constraint(equalTo: view.widthAnchor),
            hostingController.view.heightAnchor.constraint(equalTo: view.heightAnchor),
            hostingController.view.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            hostingController.view.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        ])
    }
    
    private func translucent() -> CGFloat {
        if (translucentEffect == .opaque) {
            return 1.0
        } else if (translucentEffect == .ultrathick) {
            return 0.95
        } else if (translucentEffect == .thick) {
            return 0.9
        } else if (translucentEffect == .regular) {
            return 0.85
        } else if (translucentEffect == .prominent) {
            return 0.8
        } else if (translucentEffect == .thin) {
            return 0.75
        } else if (translucentEffect == .ultrathin) {
            return 0.7
        } else {
            return 1.0
        }
    }
}

enum TranslucentEffect {
    case opaque
    case ultrathick
    case thick
    case regular
    case prominent
    case thin
    case ultrathin
}

Hi,

I wanted to use this code for coding Today Extentions (widget) that should use SwiftUI views.

My code :
`import UIKit
import NotificationCenter
import SwiftUI

class TodayViewController: UIViewController, NCWidgetProviding {

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
}
    
@IBSegueAction func addSwiftUIView(_ coder: NSCoder) -> UIViewController? {
    // Initialises BlurredHostingController
    let blurredHostingController = BlurredHostingController()

    // Sets the Hosting View for the SwiftUI View Logic
    blurredHostingController.hostingController = UIHostingController(coder: coder, rootView: WidgetMainView().environmentObject(ChronoState()))

    // Blur Tweaks for blurredHostingController
    blurredHostingController.blurEffect = .systemMaterial
    blurredHostingController.translucentEffect = .ultrathin
    

    // Presents View Controller as a Modal View Controller
    self.present(blurredHostingController, animated: true, completion: nil)
    
    return blurredHostingController
    // ORIGINAL

// return UIHostingController(coder: coder, rootView: WidgetMainView().environmentObject(ChronoState()))
}
func widgetPerformUpdate(completionHandler: (@escaping (NCUpdateResult) -> Void)) {
// Perform any setup necessary in order to update the view.

    // If an error is encountered, use NCUpdateResult.Failed
    // If there's no update required, use NCUpdateResult.NoData
    // If there's an update, use NCUpdateResult.NewData
    
    completionHandler(NCUpdateResult.newData)
}

}
`

Error:
2020-04-14 21:00:41.228693+0200 Chrono Training Widget Extension[6695:1479245] Warning: Attempt to present <Chrono_Training_Widget_Extension.BlurredHostingController: 0x15b1068d0> on <Chrono_Training_Widget_Extension.TodayViewController: 0x159d06920> whose view is not in the window hierarchy! 2020-04-14 21:00:41.229276+0200 Chrono Training Widget Extension[6695:1479245] *** Terminating app due to uncaught exception 'NSGenericException', reason: 'This coder requires that replaced objects be returned from initWithCoder:' *** First throw call stack: (0x18fe24164 0x18fb38c1c 0x18fd13bb8 0x19348b984 0x193426d50 0x193bed668 0x19348b93c 0x19348bb5c 0x193426d50 0x193be8638 0x193beb200 0x1940d9ca4 0x1940d9b3c 0x1940da924 0x1940dab78 0x1940dae78 0x193902d80 0x19390330c 0x1a43e3928 0x1938fe36c 0x193902f20 0x1a43e331c 0x194331bb0 0x18fe2ad14 0x18fcf3de8 0x18fcf4a10 0x19433af44 0x18fe285d4 0x18fe2ab60 0x18fe2ad14 0x18fcf3de8 0x18fcf4a10 0x194322ab0 0x18fe285d4 0x18fe2ab60 0x18fe2ad14 0x18fcf3de8 0x18fcf4a10 0x18fe285d4 0x18fe2ab60 0x18fe2ad14 0x18fcf3de8 0x18fac433c 0x18fac70d4 0x1950d12b4 0x1950d0f60 0x1950d14cc 0x18fd9f860 0x18fd9f7b4 0x18fd9ef04 0x18fd99ca4 0x18fd99660 0x19a1aa604 0x193f6e15c 0x18fa37fd4 0x18fa22c48 0x18fa253ac 0x190120768 0x19d60fb04 0x19d60f7f8 0x19d60ff24 0x19030bfa0 0x18fc151ec) libc++abi.dylib: terminating with uncaught exception of type NSException

I don't know why the need to call initWithCoder ?

I dont know why it would since its just a UIViewController that is a container for the SwiftUI, nothing special about it, but what I can say is that Ive only used UIHostingControllers in the addSwiftUIView() but I'd suggest add a coder in the BlurredHostingController() inside addSwiftUIView() like this BlurredHostingController(coder: coder) see if that works