Efficient way to model the data for SwiftUI - swiftui

Question

I am exploring SwiftUI+Combine with a demo app BP Management.
Homescreen has a provision to take bp readings(systolicBP, diastolicBP, pulse & weight).
Button "Next" is enabled only when all 4 fields are filled.
control should fall to the next textfield when a valid input is entered. (input is valid when it falls between the range specified by the placeholder - refer the image below)
On tapping next, on the detail screen user can edit the bp values (taken in the HomeScreen), additionally he can add recorded date, notes...
Thought enums would be best model this so I proceeded like
enum SBPInput: CaseIterable {
//name is a Text to indicate the specific row
typealias Field = (name: String, placeholder: String)
case spb, dbp, pulse, weight, note, date
var field: Field {
switch self {
case .dbp: return ("DBP", "40-250")
case .spb: return ("SBP", "50-300")
case .pulse: return ("Pulse", "40-400")
case .weight: return ("Weight", "30-350")
case .note: return ("Note", "")
case .date: return ("", Date().description)
}
}
// Here I am getting it wrong, - I can't bind a read only property
var value: CurrentValueSubject<String, Never> {
switch self {
case .date:
return CurrentValueSubject<String, Never>(Date().description)
case .spb:
return CurrentValueSubject<String, Never>("")
case .dbp:
return CurrentValueSubject<String, Never>("")
case .pulse:
return CurrentValueSubject<String, Never>("")
case .weight:
return CurrentValueSubject<String, Never>("70")
case .note:
return CurrentValueSubject<String, Never>("")
}
}
}
class HomeViewModel: ObservableObject {
#Published var aFieldsisEmpty: Bool = true
var cancellable: AnyCancellable?
var dataSoure = BPInput.allCases
init() {
var bpPublishers = (0...3).map{ BPInput.allCases[$0].value }
//If a field is empty, we need to disable "Next" button
cancellable = Publishers.CombineLatest4(bpPublishers[0], bpPublishers[1], bpPublishers[2], bpPublishers[3]).map { $0.isEmpty || $1.isEmpty || $2.isEmpty || $3.isEmpty }.assign(to: \.aFieldsisEmpty, on: self)
}
}
The idea is to create HStacks for each datasorce(sbp,dbp,pulse,weight) to look like this
struct HomeScreen: View {
#ObservedObject var viewModel = HomeViewModel()
var body: some View {
VStack {
ForEach(Range(0...3)) { index -> BPField in
BPField(input: self.$viewModel.dataSoure[index])
}
Button("Next", action: {
print("Take to the Detail screen")
}).disabled(self.viewModel.aFieldsisEmpty)
}.padding()
}
}
struct BPField: View {
#Binding var input: BPInput
var body: some View {
//implicit HStack
Text(input.field.name)
BPTextField(text: $input.value, placeHolder: input.field.name)//Error:- Cannot assign to property: 'value' is a get-only property
// input.value being read only I can't bind it. How to modify my model now so that I can bind it here?
}
}
And my custom TextField
struct BPTextField: View {
let keyboardType: UIKeyboardType = .numberPad
var style: some TextFieldStyle = RoundedBorderTextFieldStyle()
var text: Binding<String>
let placeHolder: String
// var onEdingChanged: (Bool) -> Void
// var onCommit: () -> ()
var background: some View = Color.white
var foregroundColor: Color = .black
var font: Font = .system(size: 14)
var body: some View {
TextField(placeHolder, text: text)
.background(background)
.foregroundColor(foregroundColor)
.textFieldStyle(style)
}
}

Answer 1

your problems are not there, what SwiftUI tells you.
but you should first compile "small parts" of your code and simplify it, so the compiler will tell you the real errors.
one is here:
BPTextField(text: self.$viewModel.dataSoure[index].value, placeHolder: viewModel.dataSoure[index].field.placeholder)
and the error is:
Cannot subscript a value of type 'Binding<[BPInput]>' with an argument of type 'WritableKeyPath<_, _>'
and of course you forgot the self ....