manage split view column visibility

LeCountdown/Model/NSManagedContext+Extensions.swift

@@ -37,6 +37,11 @@ extension NSManagedObjectContext {
         return try self.fetch(request)
     }
     
+    func count(entityName: String) throws -> Int {
+        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
+        return try self.count(for: fetchRequest)
+    }
+    
 }
 
 extension NSManagedObject {

LeCountdown/Views/HomeView.swift

@@ -58,14 +58,16 @@ struct RegularHomeView: View {
 
     @State private var tabSelection: Int = 1
     
+    @State private var columnVisibility: NavigationSplitViewVisibility = .detailOnly
+    
     var body: some View {
         
-        NavigationView {
+        NavigationSplitView(columnVisibility: $columnVisibility) {
             PresetsView(tabSelection: $tabSelection)
                 .environment(\.managedObjectContext, viewContext)
                 .tabItem { Label("Presets", systemImage: "globe") }
                 .tag(0)
-
+        } detail: {
             TabView(selection: $tabSelection) {
                 ContentView<AbstractTimer>()
                     .environment(\.managedObjectContext, viewContext)
@@ -78,12 +80,28 @@ struct RegularHomeView: View {
                     .tag(2)
             }.tabViewStyle(.page(indexDisplayMode: .never))
         }
+        .onAppear {
+            self._setColumnVisibility()
+        }
         .onContinueUserActivity(Shortcut.newCountdown.rawValue, perform: _handleNewCountdown)
         .onOpenURL { _ in
             self.tabSelection = 1
         }
     }
     
+    fileprivate func _setColumnVisibility() {
+        do {
+            let count = try viewContext.count(entityName: "AbstractTimer")
+            if count > 0 {
+                self.columnVisibility = .detailOnly
+            } else {
+                self.columnVisibility = .automatic
+            }
+        } catch {
+            Logger.error(error)
+        }
+    }
+    
     fileprivate func _handleNewCountdown(_ userActivity: NSUserActivity) {
         print(">>> new countdown")
     }