URLImage_modifiers.swift

struct URLImage : View {
  
    // ...

    var body: some View {
        if let image = imageLoader.image {
            return image
                .onAppear {}
                .onDisappear {}
        }
        else {
            return placeholder
                .onAppear {
                    self.imageLoader.load()
                }
                .onDisappear {
                    self.imageLoader.cancel()
                }
        }
    }
}