Converting Color and BackgroundStyle in SwiftUI

Question

I'm trying to do this where a background modifier could either accept an optional BackgroundStyle or a Color.

struct ContentView: View {
    var background: BackgroundStyle?
    var body: some View {
        VStack {
            Image(systemName: "globe")
                .imageScale(.large)
                .foregroundStyle(.tint)
            Text("Hello, world!")
        }
        .background(background ?? Color.gray)
        .padding()
    }
}

#Preview {
    ContentView(background: .background)
}

I get this error and I'm not sure how to resolve it.

Cannot convert value of type 'Color' to expected argument type 'BackgroundStyle'

Answer 1

You can use AnyShapeStyle to erase the types, converting both Color and BackgroundStyle to AnyShapeStyle.

.background(background.map(AnyShapeStyle.init) ?? AnyShapeStyle(Color.gray))

The optional here makes this a bit messy. I would use a Bool instead, to indicate whether to use the background style. There is only one instance of BackgroundStyle, anyway.

let useDefaultBackground: Bool

...

.background(
    useDefaultBackground ? AnyShapeStyle(.background) : AnyShapeStyle(Color.gray)
)