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Xcode – How to mock #Preview with a view expecting an Error as parameter?

I have a view showing error information which is working fine. The information is wrapped inside a struct. But I couldn’t figure out how to mock the expected data to show the view in preview canvas.

Struct to store the error information.

struct ErrorWrapper: Identifiable {
    let id = UUID()
    let error: Error
    let guidance: String
    let errorStyle: ErrorStyle
}

Preview with the missing part for the Error.

#Preview {
    //how to instanciate an error?
    static var errorWrapper = ErrorWrapper(error, "guidance", ErrorStyle.ok)
    ErrorViewOk(errorWrapper: errorWrapper)
}
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2

Answers


  1. Chosen as BEST ANSWER
    0

    Alternatively I was able to solve the problem not using the #Preview macro.

    struct ErrorViewOk_Preview: PreviewProvider {
enum MockError: Error {
    case invalidData
}
static var errorWrapper = ErrorWrapper(error: MockError.invalidData, guidance: "guidance", errorStyle: ErrorStyle.ok)

static var previews: some View {
    ErrorViewOk(errorWrapper: errorWrapper)
}

    }


  2. 0

    Error is a protocol so you can create a mock concrete type for it, something like:

    enum MockError: Error {
    case invalidData
}

#Preview {
    ContentView(error: ErrorWrapper(MockError.invalidData,
                                    "Halo",
                                    ErrorStyle.ok))
}
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