UIHostingConfiguration for iOS 14 & 15

BPHostingConfiguration.swift

import UIKit
import SwiftUI

struct BPHostingConfiguration<Content: View>: UIContentConfiguration {
    fileprivate let content: Content
    
    init(@ViewBuilder content: () -> Content) {
        self.content = content()
    }
    
    func makeContentView() -> any UIView & UIContentView {
        HostingView<Content>(configuration: self)
    }
    
    func updated(for state: any UIConfigurationState) -> BPHostingConfiguration {
        return self
    }
}

fileprivate final class HostingView<Content: View>: UIView, UIContentView {
    private let hostingController: UIHostingController<Content>
    private var _configuration: BPHostingConfiguration<Content>
    
    var configuration: any UIContentConfiguration {
        @storageRestrictions(initializes: _configuration, hostingController)
        init(newValue) {
            let configuration: BPHostingConfiguration<Content> = newValue as! BPHostingConfiguration<Content>
            _configuration = configuration as! BPHostingConfiguration
            hostingController = .init(rootView: configuration.content)
        }
        get {
            _configuration
        }
        set {
            let configuration: BPHostingConfiguration<Content> = newValue as! BPHostingConfiguration<Content>
            _configuration = configuration
            hostingController.rootView = configuration.content
        }
    }
    
    
    init(configuration: any UIContentConfiguration) {
        self.configuration = configuration
        super.init(frame: .null)
        
        let hostingView: UIView = hostingController.view
        hostingView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        addSubview(hostingView)
    }
    
    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

Example

import UIKit
import SwiftUI

class CollectionViewController: UICollectionViewController {
    private let cellRegistration: UICollectionView.CellRegistration<UICollectionViewListCell, NSNull> = .init { cell, indexPath, itemIdentifier in
        cell.contentConfiguration = BPHostingConfiguration  { 
            Text(indexPath.description)
        }
    }
    
    init() {
        let listConfiguration: UICollectionLayoutListConfiguration = .init(appearance: .insetGrouped)
        let collectionViewLayout: UICollectionViewCompositionalLayout = .list(using: listConfiguration)
        super.init(collectionViewLayout: collectionViewLayout)
    }
    
    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }


    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 300
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        return collectionView.dequeueConfiguredReusableCell(using: cellRegistration, for: indexPath, item: nil)
    }
}