Custom UIKit view with child SwiftUI views

playground.swift

import UIKit
import SwiftUI
import PlaygroundSupport

// CustomParentView is a custom UIKit view. Its Coordinator can be used
// to manage delegates if needed (e.g. UIContextMenuInteractionDelegate).

struct CustomParentView<Content: View>: UIViewRepresentable {
    let content: UIView
    
    @inlinable init(@ViewBuilder content: () -> Content) {
        self.content = UIHostingController(rootView: content()).view
    }

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    func makeUIView(context: Context) -> UIView {
        let view = UIView()
        view.backgroundColor = .lightGray
        
        content.frame = view.bounds
        content.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        content.backgroundColor = .clear // unfortunate
        view.addSubview(content)

        return view
    }

    func updateUIView(_ uiView: UIView, context: Context) {
        // nothing to update
    }

    class Coordinator: NSObject {
        var view: CustomParentView

        init(_ view: CustomParentView) {
            self.view = view
        }
    }
}

// ContentView is an example of how to use our CustomParentView
// with child SwiftUI views.

struct ContentView: View {
    var body: some View {
        CustomParentView {
            Text("Test")
                .foregroundColor(.white)
        }
    }
}

let viewController = UIHostingController(rootView: ContentView())
PlaygroundPage.current.liveView = viewController