FB16360042: SwiftUI @FocusedValue needs to provide a binding through projectedValue when given a Observable class

[sindresorhus]

• Date: 2025-01-19
• Resolution: Open
• Area: SwiftUI
• OS: macOS 15.2
• Type: Incorrect/Unexpected Behavior

Description

When using a class with ObservableObject, we could use @FocusedObject and access its projectedValue through $ to get a binding. The replacement for @FocusedObject when using @Observable is @FocusedValue, but it does not have a projectedValue ($), so there is no way to get a binding to the class.

I previously had this with ObservableObject:

struct MenuToggle: View {
	@FocusedObject private var sceneData: SceneData?

	var body: some View {
		Toggle(
			"Unicorn",
			isOn: $sceneData?.isUnicorn ?? .constant(false)
		)
	}
}

I assumed I could move to this when using @Observable:

struct MenuToggle: View {
	@FocusedValue(SceneData.self) private var sceneData

	var body: some View {
		Toggle(
			"Unicorn",
			// No binding available...
			isOn: $sceneData?.isUnicorn ?? .constant(false)
		)
	}
}

But it does not provide a binding through $... It should!

---

As a workaround, I passed the binding into a FocusedScene value, but that doesn't seem like the proper solution.

struct MenuToggle: View {
	@FocusedValue(\.sceneData) private var sceneData

	var body: some View {
		Toggle(
			"Unicorn",
			isOn: sceneData?.isUnicorn ?? .constant(false)
		)
	}
}

extension FocusedValues {
	@Entry
	var sceneData: Binding<SceneData>?
}

---

For context, the ?? in the examples work with the binding because I have this:

extension Binding {
	static func ?? <T>(lhs: Binding<T?>, rhs: T) -> Binding<T> {
		.init(
			get: { lhs.wrappedValue ?? rhs },
			set: {
				lhs.wrappedValue = $0
			}
		)
	}

	static func ?? <T>(lhs: Binding<T?>, rhs: T?) -> Binding<T?> {
		.init(
			get: { lhs.wrappedValue ?? rhs },
			set: {
				lhs.wrappedValue = $0
			}
		)
	}
}