Using UIViewController via the SwiftUI Environment

UIViewController+SwiftUI.swift

struct ViewControllerHolder {
	weak var value: UIViewController?
	init(_ value: UIViewController?) {
		self.value = value
	}
}

struct ViewControllerKey: EnvironmentKey {
	static var defaultValue: ViewControllerHolder { return ViewControllerHolder(UIApplication.shared.windows.first?.rootViewController ) }
}

extension EnvironmentValues {
	var viewController: ViewControllerHolder {
		get { return self[ViewControllerKey.self] }
		set { self[ViewControllerKey.self] = newValue }
	}
}

extension UIViewController {
	func present<Content: View>(presentationStyle: UIModalPresentationStyle = .automatic, transitionStyle: UIModalTransitionStyle = .coverVertical, animated: Bool = true, completion: @escaping () -> Void = {}, @ViewBuilder builder: () -> Content) {
		let toPresent = UIHostingController(rootView: AnyView(EmptyView()))
		toPresent.modalPresentationStyle = presentationStyle
		toPresent.rootView = AnyView(
			builder()
				.environment(\.viewController, ViewControllerHolder(toPresent))
		)
		if presentationStyle == .overCurrentContext {
			toPresent.view.backgroundColor = .clear
		}
		self.present(toPresent, animated: animated, completion: completion)
	}
}

hi, we have tried to use this approach to present iPad full screen modal views but we are getting memory leaks too :/ did you find any solution or alternative?

I did not look into it further as I couldn't get Timothy's updated code to build and our design changed enough that we didn't need it. Sorry. Please post here if you do find a solution because I'm sure this will come up again (!).

I put this code into a simple project, presented a UIHostingController from window.rootViewController and then did self.viewControllerHolder.value?.dismiss(...). I don't see any leaks in the memory graph after dismissal.

If you didn't directly copy and paste this, ensure that you're declaring extension EnvironmentValues { var viewController: ViewControllerHolder { ... } } and not var viewController: UIViewController? { ... } as the latter definitely will leak.

Hi! Thanks so much for the solution, I'm fairly new to swift and I was also running into the memory leak problem but once I had updated the code it seems like there is a problem while building. I ran into a key path value type mismatch error on the @Environment(.viewController) private var viewControllerHolder: UIViewController? line

do you have any idea wha could be the problem? Thanks!

@bobshoemaker wrote:

Hi! Thanks so much for the solution, I'm fairly new to swift and I was also running into the memory leak problem but once I had updated the code it seems like there is a problem while building. I ran into a key path value type mismatch error on the @Environment(.viewController) private var viewControllerHolder: UIViewController? line

do you have any idea wha could be the problem? Thanks!

The .viewController in @Environment(\.viewController) refers to the EnvironmentValues extension's var definition on line 14 of the gist. If you refer to that you will see that it is defined as a ViewControllerHolder, not a UIViewController.
(Also you are missing the keypath starting "" in your comment above, but I assume that is just local to this comment and not your code).

So set the type of the var to ViewControllerHolder and that may make the compiler happy (it's a compiler, so who knows? ;)).
Something like:

@Environment(\.viewController) private var viewControllerHolder: ViewControllerHolder?

Thanks! As you said it's just a compiler issue! I've just changed it to:

@Environment(\.viewController) private var viewControllerHolder: ViewControllerHolder?
private var viewController: UIViewController? {
   self.viewControllerHolder?.value
}

The memory leak is gone as well! Thanks again!

Thanks for this! I have a couple of questions

Is there a way to make the modal only as big as the content you put in it? I don’t want the white box that appears when using .formSheet/pageSheet. (I know I can just set toPresent.view.backgroundColor = .clear) preferredContentSize seems like an option but haven’t had a chance to test

Also when I tried to add a button to the body of ModalContentView to dismiss (experimenting with full screen), the button appeared behind the content, not above it like I expected given its a VStack. I can’t therefore see how to dismiss full screen

@Environment(\.viewController) private var viewControllerHolder: ViewControllerHolder?
private var viewController: UIViewController? {
   self.viewControllerHolder?.value
}

with this code I'm getting error like
Key path value type 'ViewControllerHolder' cannot be converted to contextual type 'ViewControllerHolder?

@Sadmansamee

@Environment(\.viewController) private var viewControllerHolder: ViewControllerHolder?
private var viewController: UIViewController? {
   self.viewControllerHolder?.value
}

with this code I'm getting error like

Key path value type 'ViewControllerHolder' cannot be converted to contextual type 'ViewControllerHolder?

Don't have time to test this but maybe try:

@Environment(\.viewController) private var viewControllerHolder: ViewControllerHolder
private var viewController: UIViewController? {
    self.viewControllerHolder.value
}

Reading the gist, Line 14 defines viewController to return a non-optional ViewControllerHolder so I'm guessing that's the issue you're running into.

and how to dismiss it

its support for RTL?