SwiftUI `withAnimation` doesn't work with `inout` parameter - swift

Question

I'm writing an inspector view mocking macOS Sidebar behavior in SwiftUI. It use .transition(.move(edge: .trailing)) only when the whole view appear and disappear but doesn't when switching between inner views. Here's the demo.
So I come up with following code. Selection is an enum representing views one-to-one which always starts with case none. inspect() method is used for change selection value and determining if using animation (remember I mentioned not to use animation when switching between inner views). I attach my full code at the end.
However, there'll never be any animation applied. How can I fix this?
If I use this more specific one that uses #State selection directly in inspect() method, the animation comes back, but cannot reuse the code if I have another Inspector, like #State var selection2: Selection2.
func inspect(to target: Selection) {
if target.rawValue == 0 {
withAnimation {
selection = target
}
} else {
if selection.rawValue == 0 {
withAnimation {
selection = target
}
} else {
selection = target
}
}
}
Here comes my full code:
struct ContentView: View {
enum Selection: Int {
case none
case view1
case view2
case view3
}
#State var selection: Selection = .none
func inspect<Selection: RawRepresentable<Int>>(_ selection: inout Selection, to target: Selection) {
if target.rawValue == 0 {
withAnimation {
selection = target
}
} else {
if selection.rawValue == 0 {
withAnimation {
selection = target
}
} else {
selection = target
}
}
}
var body: some View {
HStack {
VStack {
Button("None") {
inspect(&selection, to: .none)
}
Button("View 1") {
inspect(&selection, to: .view1)
}
Button("View 2") {
inspect(&selection, to: .view2)
}
Button("View 3") {
inspect(&selection, to: .view3)
}
}
Group {
if selection.rawValue == 1 {
Text("Hello 1")
} else if selection.rawValue == 2 {
Text("Hello 2")
} else if selection.rawValue == 3 {
Text("Hello 3")
}
}
.transition(.move(edge: .trailing))
}
}
}

Answer 1

Your code looks a bit to complicated so I have simplified it and if I understood what you want to do correctly it also behaves as expected.
First I made use of the #State property directly in the inspect function thus removing the need to pass it as an argument and also generics is not needed here
func inspect(to target: Selection) {
if target == .none {
withAnimation {
selection = target
}
} else {
if selection == .none {
withAnimation {
selection = target
}
} else {
selection = target
}
}
}
As seen above I am using the enum cases directly and not any raw value, as a matter of fact I removed that from the enum
enum Selection {
case none
case view1
case view2
case view3
}
and also change the code in the Group because of this
Group {
if selection == .view1 {
Text("Hello 1")
} else if selection == .view2 {
Text("Hello 2")
} else if selection == .view3 {
Text("Hello 3")
}
}
Overall I think this makes the code cleaner and easier to read.