Accessing UIHostingController from a SwiftUI view

While I was working on a mixed UIKit and SwiftUI project, I needed a way to access the UIHostingController within the SwiftUI view so that I could use it for interacting with other UIKit methods. This blog post tackles the problem and provides a simple solution how to implement it.

The approach we are taking is using the SwiftUI environment and inserting an object into the environment, which then keeps a weak reference to the view controller hosting the SwiftUI view. Using the SwiftUI view environment has a benefit of allowing multiple other SwiftUI views within the hierarchy to use it as well. In the end, we would like to write something like this:

	// Presenting the detail view using UIKit presentation methods
	let hostingController = DetailView().embeddedInHostingController()
	presentingViewController.present(hostingController, animated: true)
	// The view which needs access to the view controller hosting it
	struct DetailView: View {
	@EnvironmentObject var hostingProvider: ViewControllerProvider
	var body: some View {
	VStack {
	Text("Detail")
	Button("Access View Controller") {
	let viewController = hostingProvider.viewController
	// … do something with the view controller
	}
	}
	}
	}

view raw DetailView.swift hosted with ❤ by GitHub

In the snippet above, we use a custom embeddedInHostingController() function which inserts a new ViewControllerProvider type the to the environment. Let’s take a closer look how this function and type are implemented.

	extension View {
	func embeddedInHostingController() -> UIHostingController<some View> {
	let provider = ViewControllerProvider()
	let hostingAccessingView = environmentObject(provider)
	let hostingController = UIHostingController(rootView: hostingAccessingView)
	provider.viewController = hostingController
	return hostingController
	}
	}
	final class ViewControllerProvider: ObservableObject {
	fileprivate(set) weak var viewController: UIViewController?
	}

view raw ViewControllerProvider.swift hosted with ❤ by GitHub

The ViewControllerProvider class keeps a weak reference to the view controller. Since UIHostingController is a subclass of UIViewController we can just use UIViewController as a type. The embedded function creates an instance of the provider and a hosting controller, inserts the provider into the SwiftUI view environment and then sets the weak property which we can access later.

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