Xcode 11 -- SwiftUI's dark mode setup

This is probably a bug in this beta release of Xcode 11. I tried the dark mode feature in a UIKit application and it is working perfectly using UIColor but the same color wouldn’t work using Color in SwiftUI. Hopefully this will be fixed in the next releases.

---

Update: This issue was fixed with Xcode 11 beta 3.

A working (but quite verbose) solution we can use to overcome this current limitation is to extend Color with methods parameterised with the current color scheme as follows:

import SwiftUI

extension Color {

    static let lightBackgroundColor = Color(white: 1.0)

    static let darkBackgroundColor = Color(white: 0.0)

    static func backgroundColor(for colorScheme: ColorScheme) -> Color {
        if colorScheme == .dark {
            return darkBackgroundColor
        } else {
            return lightBackgroundColor
        }
    }
}

And in the views where you need to access these colors you would add an environment property for the color scheme and use it to retrieve the dynamic color:

import SwiftUI

struct ColoredView : View {

    @Environment(\.colorScheme) var colorScheme: ColorScheme

    var body: some View {
        Rectangle().fill(Color.backgroundColor(for: self.colorScheme))
    }
}

These colours defined in code work for Xcode previews as well as the simulator.