Convert Binding to UIBinding

[maximkrouk]

Currently I'm using a workaround:

public struct UIBindingView<Value: Equatable, Content: View>: View {
	@UIBinding
	private var downstream: Value

	@Binding
	private var upstream: Value

	private let content: (UIBinding<Value>) -> Content

	public init(
		_ value: Binding<Value>,
		@ViewBuilder content: @escaping (UIBinding<Value>) -> Content
	) {
		self.downstream = value.wrappedValue
		self._upstream = value
		self.content = content
	}

	public var body: some View {
		content($downstream[setter: .onDidSet(
			perform: { newValue in
				if upstream != newValue { upstream = newValue }
			}
		)])
		.onChange(of: upstream, initial: true) { _, newValue in
			if downstream != newValue { downstream = newValue }
		}
	}
}

struct MyView {
  @Binding
  var someValue: Float

  var body: some View {
    UIBindingView($someValue) { binding in
      SomePicker(value: binding)
    }
  }
}

Note

onDidSet is injected through dynamic member lookup with swift-keypath-mapping [setter:] subscript

I just figured out this approach and I think I had a few weird moments related to values sync (still testing, I have a scrollable picker that sends fractional values pretty frequently, tho all the values are rounded to .2f). Probably it's related to willSet/didSet sync and could be resolved with replacing setter to .onWillSet or using both (.perform(onWillSet:onDidSet:)) and an internal TaskLocal Bool that can be checked in onChange

However maybe there is just a simpler way to convert Binding to UIBinding 🤔

There was a discussion related to conversion in other direction #280, however it's related to TCA rather than swift-navigation. It's understandable that it's possible to derive both types of bindings from an Observable object, but in my case an Observable object (a TCA Store 🙂) is declared in higher-level feature module, and the component has to be declared in lower-level AppUI module. And I'd like to avoid exposing UIBinding from SwiftUI component 🫠

UPD:

This seem to work correctly and without any visual artifacts:

// Some more usage context:
//
// My picker accepts a collection of values identified by Int (0...100)
// I also replaced my selection mapping from Int($0 * 100) to Int(round($0 * 100))
public struct UIBindingView<Value: Equatable, Content: View>: View {
	@UIBinding
	private var downstream: Value

	@Binding
	private var upstream: Value

	private let content: (UIBinding<Value>) -> Content

	public init(
		_ value: Binding<Value>,
		@ViewBuilder content: @escaping (UIBinding<Value>) -> Content
	) {
		self.downstream = value.wrappedValue
		self._upstream = value
		self.content = content
	}

	public var body: some View {
		content($downstream[
			setter: .inline { value, newValue in
				UIBindingViewTaskLocals.$isUpdating.withValue(true) {
					value = newValue
					if upstream != newValue { upstream = newValue }
				}
			}
		])
		.onChange(of: upstream, initial: true) { oldValue, newValue in
			guard
				!UIBindingViewTaskLocals.isUpdating,
				downstream != newValue
			else { return }
			self.downstream = newValue
		}
	}
}

fileprivate enum UIBindingViewTaskLocals {
	@TaskLocal
	static var isUpdating = false
}

But more direct conversion tips are still appreciated