Dismiss @Presents modal but keep state?

[zachwaugh]

I'm presenting a custom image picker sheet with an optional state using @Presents var imagePicker: ImagePicker.State? When the user selects an image, I want to dismiss the sheet (state.imagePicker = nil), but I also want to keep that state around so if they pick another image, they'll be in the same place they were before.

A simplified version of what I'm doing now is something like this:

struct State {
  @Presents var imagePicker: ImagePicker.State?
  var lastImagePicker: ImagePicker.State?
}

// reducer
case .selectImageButtonTapped:
  state.imagePicker = state.lastImagePicker ?? ImagePicker.State()

case .selectImage(let image):
  state.lastImagePicker = state.imagePicker
  state.imagePicker = nil

That works, but curious if there is a better way without having to keep that redundant state around and having to manage that myself?

[stephencelis]

@Presents is state-driven, so the nil vs. non-nil state of the wrapped value is what tells SwiftUI to hide vs. show a feature. If you want this state to stick around, you could hold onto the imagePicker as a non-optional, Scope-d child, instead, and then drive navigation using a simple boolean, instead.

If you have multiple destinations, you can remove the associated value from that case, instead. Here's an example refactor of our SyncUps app's detail feature where it preserves the edit "draft":

diff --git a/Examples/SyncUps/SyncUps/SyncUpDetail.swift b/Examples/SyncUps/SyncUps/SyncUpDetail.swift
index b321ee54ac..cecb6fcba9 100644
--- a/Examples/SyncUps/SyncUps/SyncUpDetail.swift
+++ b/Examples/SyncUps/SyncUps/SyncUpDetail.swift
@@ -6,7 +6,7 @@ struct SyncUpDetail {
   @Reducer(state: .equatable)
   enum Destination {
     case alert(AlertState<Alert>)
-    case edit(SyncUpForm)
+    case edit
 
     @CasePathable
     enum Alert {
@@ -19,7 +19,14 @@ struct SyncUpDetail {
   @ObservableState
   struct State: Equatable {
     @Presents var destination: Destination.State?
+    var edit: SyncUpForm.State
     @Shared var syncUp: SyncUp
+
+    init(destination: Destination.State? = nil, syncUp: Shared<SyncUp>) {
+      self.destination = destination
+      self.edit = SyncUpForm.State(syncUp: syncUp.wrappedValue)
+      self._syncUp = syncUp
+    }
   }
 
   enum Action: Sendable {
@@ -29,6 +36,7 @@ struct SyncUpDetail {
     case deleteMeetings(atOffsets: IndexSet)
     case destination(PresentationAction<Destination.Action>)
     case doneEditingButtonTapped
+    case edit(SyncUpForm.Action)
     case editButtonTapped
     case startMeetingButtonTapped
 
@@ -43,6 +51,9 @@ struct SyncUpDetail {
   @Dependency(\.speechClient.authorizationStatus) var authorizationStatus
 
   var body: some ReducerOf<Self> {
+    Scope(state: \.edit, action: \.edit) {
+      SyncUpForm()
+    }
     Reduce { state, action in
       switch action {
       case .cancelEditButtonTapped:
@@ -78,14 +89,16 @@ struct SyncUpDetail {
         return .none
 
       case .doneEditingButtonTapped:
-        guard case let .some(.edit(editState)) = state.destination
-        else { return .none }
-        state.syncUp = editState.syncUp
+        guard state.destination.is(\.edit) else { return .none }
+        state.syncUp = state.edit.syncUp
         state.destination = nil
         return .none
 
+      case .edit:
+        return .none
+
       case .editButtonTapped:
-        state.destination = .edit(SyncUpForm.State(syncUp: state.syncUp))
+        state.destination = .edit
         return .none
 
       case .startMeetingButtonTapped:
@@ -188,9 +201,9 @@ struct SyncUpDetailView: View {
     .alert($store.scope(state: \.destination?.alert, action: \.destination.alert))
     .sheet(
       item: $store.scope(state: \.destination?.edit, action: \.destination.edit)
-    ) { editSyncUpStore in
+    ) { _ in
       NavigationStack {
-        SyncUpFormView(store: editSyncUpStore)
+        SyncUpFormView(store: store.scope(state: \.edit, action: \.edit))
           .navigationTitle(store.syncUp.title)
           .toolbar {
             ToolbarItem(placement: .cancellationAction) {

[zachwaugh]

Gotcha, that makes sense, thank you!