swift - Custom Trait with UITraitBridgedEnvironmentKey not writing back to UITraitCollection - Stack Overflow

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I'm trying to create a custom UI trait and a matching bridged SwiftUI environment key in my SwiftUI App.

I want to override the environment key in a swift view and then have that reflect in the current UITraitCollection.

I'm following the pattern in the linked video but am not seeing the changes reflect in the current trait collection when I update the swift env value.

Does anyone know what I am missing?

// Setup
enum CustomTheme: String, Codable {
    case theme1 = “theme1”,
         theme2 = “theme2”
}
 
struct customThemeTrait: UITraitDefinition {
    static let defaultValue = brand.theme1
    static let affectsColorAppearance = true
    static let identifier = "com.appName.customTheme"
    
}
extension UITraitCollection {
    var customTheme: CustomTheme { self[customThemeTrait.self] }
}
extension UIMutableTraits {
    var customTheme: CustomTheme {
        get { self[customThemeTrait.self] }
        set { self[customThemeTrait.self] = newValue }
    }
}
 
private struct customThemeKey: EnvironmentKey {
    static let defaultValue: CustomTheme = .theme1
}
 
extension customThemeKey: UITraitBridgedEnvironmentKey {
    static func read(from traitCollection: UITraitCollection) -> CustomTheme {
        traitCollection.customTheme
    }
    static func write(to mutableTraits: inout UIMutableTraits, value: CustomTheme) {
        mutableTraits.customTheme = value
    }
}
extension EnvironmentValues {
    var customTheme: CustomTheme {
        get { self[customThemeKey.self] }
        set { self[customThemeKey.self] = newValue }
    }
}
 
 
 
// Attempted Usage
 
extension Color {
    static func primaryBackground() -> Color {
        UITraitCollection.current.customTheme == .theme1 ? Color.red : Color.blue
    }
}
 
struct ContentView: View {
    @State private var theme = .theme1
 
    var body: some View {
        if (dataHasLoaded && themeIsSet) {
            HomeView()
            .environment(\.customTheme, theme)
        } else {
            SelectThemeView( theme: self.theme, setContentThemeHandler)
        }
    }
 
    func setContentThemeHandler(theme: customTheme) { 
        self.theme = theme
    }
}
 
 
struct HomeView() {
    @Environment(\.customTheme) private var currentTheme: customTheme    
var body: some View {
        VStack {
            Text("currentTheme: \(currentTheme.rawValue)")
                .background(Color.primaryBackground())
            Text("currentUITrait: \(UITraitCollection.current.customTheme.rawValue)")
                .background(Color.primaryBackground())
        }
    }
}
 

OUTCOME: After selecting theme2 in the theme selector view and navigating to the homeView, the background is still red and the env and trait values print the following:

currentTheme: theme2

currentUITrait: theme1 //<-- Not goals

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