Enum reducer and .sheet(item:onDismiss:content:): Make cases have different ID

[jessedoescode]

Hey! Apple's docs on sheet(item:onDismiss:content:) state on the item:

If item changes, the system dismisses the sheet and replaces it with a new one using the same process.

However, if I'm doing:

@Reducer(state: .equatable)
    enum Sheet {
        case featureA(FeatureA)
        case featureB(FeatureB)
    }

sheet(item: $store.scope(state: \.sheet, action: \.sheet)) { store in
            let _ = print("createMenuSheet", store.id)
            switch store.case {
            case let .featureA(store):
                FeatureA(store: store)
            case let .featureB(store):
                FeatureB(store: store)

SwiftUI won't recognize a change to the enum case and won't animate the sheet disappearing and reappearing with the new content, as the id handled by scoped store remains the same? Or have I omitted something. The behaviour I'm seeing is that the sheet content does change, but the sheet does not dismiss and reappear, but instead stays open constantly.

Thank you!

[lukeredpath]

This seems like the expected behaviour to me - you're using a single .sheet modifier with an item that is the store scoped to the sheet value. Try using two .sheet modifiers with each scoped to the appropriate case instead (e.g. state: \.sheet?.featureA, action: .sheet.featureA)`).

[jessedoescode]

@lukeredpath Thanks! When using a bare enum conforming to Identifiable, SwiftUI does animate sheet dismissal and reappear on case change, even when using a single .sheet modifier, so I was wondering.

enum State: String, Identifiable {
    case featureA = "A"
    case featureB = "B"
    
    var id: String {
        self.rawValue
    }
}

.sheet(item: $state) { state in
                switch state {
                case .featureA:
                    Text("Feature A")
                case .featureB:
                    Text("Feature B")
                }
            }

But using multiple .sheet modifiers is a valid workaround 👍

[lukeredpath]

Yes, this will work but its very different to passing in a reference to a store - in your second example $state is a binding to a value so SwiftUI can easily tell when its value has changed, where as in the first example the item will always be a Store<Sheet.State?, Sheet.Action>. Perhaps it would be possible for the store to derive a unique ID when its State conforms to identifiable, I don't know.

[mbrandonw]

We do have a PR to derive store identity from the state's identity: #3464. But more needs to be explored before that can be ready to merge.

Until then you can always conform Sheet.State to be identifiable and then use the sheet(item:id:) method that comes with SwiftUINavigation (which is included in TCA automatically):

extension Sheet.State: Identifiable {
  var id: AnyHashable { … }
}

// in the view:
.sheet(item: $store.scope(state: \.sheet, action: \.sheet), id: \.id) { store in
  …
}