Short answer you cannot. Because @State wrapper is not intended for this. I cannot recall now a nice work around for this issue. But if I will, I will post update here. As a quick fix you may want to try to do like so:

@State var imagesM = [String]() // Basically leave it empty

then use

.onAppear {
  imagesM = fetchImageURLs() // but again this shouldn't be heavy task
}

Here's my code: 😎 😎 😎

@State private var myValue: Int = 0

@MyPropertyWrapper var computedValue: Int { return myValue * 2 }