Is there a way to create a binding off a computed array property in an enum at a particular index in SwiftUI? - binding

Question

I'm modelling view state in my viewModel using an enum...
enum ViewState<T> {
case idle
case error(Error)
case loading
case data([T])
I have a computed property to get the data
var data: [T] {
guard case let .data(data) = self else {
return []
}
return data
}
In one of my views I iterate through the data
var dropdownListView: some View {
ForEach(viewModel.state.data.indices, id: \.self) { index in
DropdownView(
viewModel: $viewModel.state.data[index],
isActionSheetPresented: $viewModel.isActionSheetPresented
)
}.eraseToAnyView()
}
I get an error as you can't make a binding from a computed property so make my own custom binding...
ForEach(viewModel.state.data.indicies, id: \.self) { index in
DropdownView(viewModel: Binding<ItemViewModel>(
get: {return viewModel.state.data[index] },
set: { value in
var data = viewModel.state.data
data[index] = value
viewModel.state = .data(data)
},
isActionSheetPresented: $viewModel.isActionSheetPresented
)
}
This works but are there any issues with setting the whole state again in the binding setter (I believe SwiftUI is intelligent enough that this would be efficient) or is there another way to do this here?

Answer 1

On my vision you mixed a state and a data, which are different things. So instead of .data([T]), I would recommend something like .loaded (ie, state) and keep data by standalone #Published var data: [T] property. If that adapted your code will look much more naturally.
Like
ForEach(viewModel.data.indices, id: \.self) { index in
DropdownView(
viewModel: $viewModel.data[index],
isActionSheetPresented: $viewModel.isActionSheetPresented
)
}//.eraseToAnyView() // << you don't need this
}