Initializers with different stored properties - swift

Question

I have the following view where I pass a binding to an item that I need to be selected.
struct SelectionListView<Data>: View where Data: RandomAccessCollection, Data.Element: Identifiable, Data.Element: Named {
private let data: Data
#Binding private var isPresented: Bool
#Binding private var selectedElement: Data.Element
init(
data: Data,
selectedElement: Binding<Data.Element>,
isPresented: Binding<Bool>
) {
self.data = data
_selectedElement = selectedElement
_isPresented = isPresented
}
var body: some View {
VStack {
ForEach(data) { element in
Button(element.name) {
selectedElement = element
isPresented.toggle()
}
.foregroundColor(
selectedElement.id == item.id
? .black
: .white
)
}
}
}
}
I would need a slightly different initializer of this view where I can only pass the element ID, instead of the whole element. I'm having trouble achieving this solution. To make it even more clear, it would be great if I could have a second initializer such that:
init(
data: Data,
selectedId: Binding<Data.Element.ID>,
isPresented: Binding<Bool>
)

Answer 1

Here is a working version. I decided to store the element or id in their own enum cases. I made the view separate just so it is a little easier to understand what I did.
Working code:
struct SelectionListView<Data>: View where Data: RandomAccessCollection, Data.Element: Identifiable, Data.Element: Named {
enum Selected {
case element(Binding<Data.Element>)
case id(Binding<Data.Element.ID>)
}
#Binding private var isPresented: Bool
private let data: Data
private let selected: Selected
init(
data: Data,
selectedElement: Binding<Data.Element>,
isPresented: Binding<Bool>
) {
self.data = data
selected = .element(selectedElement)
_isPresented = isPresented
}
init(
data: Data,
selectedId: Binding<Data.Element.ID>,
isPresented: Binding<Bool>
) {
self.data = data
selected = .id(selectedId)
_isPresented = isPresented
}
var body: some View {
SelectionListItem(data: data) { dataElement in
switch selected {
case .element(let element):
element.wrappedValue = dataElement
print("Selected element:", element.wrappedValue)
case .id(let id):
id.wrappedValue = dataElement.id
print("Selected element ID:", id.wrappedValue)
}
isPresented.toggle()
}
}
}
struct SelectionListItem<Data>: View where Data: RandomAccessCollection, Data.Element: Identifiable, Data.Element: Named {
let data: Data
let action: (Data.Element) -> Void
var body: some View {
VStack {
ForEach(data) { element in
Button(element.name) {
action(element)
}
.foregroundColor(
.red // Temporary because I don't know what `item.id` is
// selectedElement.id == item.id
// ? .black
// : .white
)
}
}
}
}
Other code for minimal working example:
struct ContentView: View {
#State private var selection: StrItem
#State private var selectionId: StrItem.ID
#State private var isPresented = true
private let data: [StrItem]
init() {
data = [StrItem("Hello"), StrItem("world!")]
_selection = State(initialValue: data.first!)
_selectionId = State(initialValue: data.first!.id)
}
var body: some View {
// Comment these to try each initializer
//SelectionListView(data: data, selectedElement: $selection, isPresented: $isPresented)
SelectionListView(data: data, selectedId: $selectionId, isPresented: $isPresented)
}
}
protocol Named {
var name: String { get }
}
struct StrItem: Identifiable, Named {
let id = UUID()
let str: String
var name: String { id.uuidString }
init(_ str: String) {
self.str = str
}
}

Answer 2

I'm not really sure what you are trying to achieve. Something feels off :) But anyway, here's a variant of your code that would do what you want:
struct SelectionListView<Data>: View where Data: RandomAccessCollection, Data.Element: Identifiable, Data.Element: Named {
private let data: Data
#Binding private var isPresented: Bool
#Binding private var selectedElement: Data.Element
#Binding private var selectedId: Data.Element.ID
init(
data: Data,
selectedElement: Binding<Data.Element>,
isPresented: Binding<Bool>
) {
self.data = data
_selectedElement = selectedElement
_selectedId = .constant(selectedElement.wrappedValue.id)
_isPresented = isPresented
}
init(
data: Data,
selectedId: Binding<Data.Element.ID>,
isPresented: Binding<Bool>
) {
self.data = data
_selectedElement = .constant(data.first(where: { $0.id == selectedId.wrappedValue })!)
_selectedId = selectedId
_isPresented = isPresented
}
var body: some View {
VStack {
ForEach(data) { element in
Button(element.name) {
selectedElement = element
selectedId = element.id
isPresented.toggle()
}
.foregroundColor(
selectedElement.id == element.id
? .black
: .gray
)
}
}
}
}