I am getting the following behavior:
an involuntary navigation back to the list view and then again back to the detailed view or
an involuntary navigation to another copy of the same detailed view and then back to the list view.
I am adding the code below :
abildgaard
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struct ContentView: View {
		var body: some View {
				TabView {
						NavigationView {
								TasksListView()
						}
						.tabItem {
								Image(systemName: "tray.full")
										.font(.title)
								Text("Master")
						}
						NavigationView {
								EmptyView()
						}
						.tabItem {
								Image(systemName: "magnifyingglass")
										.font(.title)
								Text("Search")
						}
				}	
		}
}
struct TasksListView: View {
		
		// NSManagedObjectContext
		@Environment(\.managedObjectContext) var viewContext
		// Results of fetch request for tasks:
		@FetchRequest(entity: Task.entity(),sortDescriptors: [NSSortDescriptor(key: "pinned", ascending: false),
																													NSSortDescriptor(key: "created", ascending: true),
																													NSSortDescriptor(key: "name", ascending: true)])
		var tasks: FetchedResults<Task>
		
		// when we create a new task and navigate to it programitically
		@State var selectionId : String?
		@State var newTask : Task?
		var body: some View {
				
				List() {
						ForEach(tasks, id: \.self) { task in
								NavigationLink(destination: DetailsView(task: task), tag: task.id!.uuidString, selection: self.$selectionId) {
										HStack() {
												VStack(alignment: .leading) {
														Text("\(task.name ?? "unknown")")
																.font(Font.headline.weight(.light))
																.padding(.bottom,5)
														Text("Created:\t\(task.created ?? Date(), formatter: Self.dateFormatter)")
																.font(Font.subheadline.weight(.light))
																.padding(.bottom,5)
														if task.due != nil {
																Text("Due:\t\t\(task.due!, formatter: Self.dateFormatter)")
																		.font(Font.subheadline.weight(.light))
																		.padding(.bottom,5)
														}
												}
										}
								}
								
						}
				}
				.navigationBarTitle(Text("Tasks"),displayMode: .inline)
				.navigationBarItems(trailing: rightButton)
		}
		
		
		var rightButton: some View {
				Image(systemName: "plus.circle")
						.foregroundColor(Color(UIColor.systemBlue))
						.font(.title)
						.contentShape(Rectangle())
						.onTapGesture {
								// create a new task and navigate to it's detailed view to add values
								Task.create(in: self.viewContext) { (task, success, error) in
										if success {
												self.newTask = task
												self.selectionId = task!.id!.uuidString
										}
								}
								
				}
		}
}
- continued
The details view:
struct DetailsView: View {
@Environment(\.managedObjectContext) var viewContext
@ObservedObject var task : Task
@State var isPinned : Bool = false
var body: some View {
List() {
Section() {
Toggle(isOn: self.$isPinned) {
Text("Pinned")
}
}
Section() {
TextField("Name", text: self.$name)
.font(Font.headline.weight(.light)
}
....
}
.navigationBarTitle(Text("Task Details"),displayMode: .inline)
.navigationBarItems(trailing: rightButton)
.listStyle(GroupedListStyle())
.onAppear() {
if self.task.pinned {
self.isPinned = true
}
}
}
var rightButton: some View {
Button("Save") {
self.task.pinned = self.isPinned
Task.save(in: self.viewContext) { (success, error) in
DispatchQueue.main.async {
....
}
}
}
}
}
extension Task {
static func save(in managedObjectContext: NSManagedObjectContext, completion: @escaping (Bool, NSError?) -> Void ) {
managedObjectContext.performAndWait() {
do {
try managedObjectContext.save()
completion(true, nil)
} catch {
let nserror = error as NSError
completion(false, nserror)
}
}
}
}
I am seeing precisely the same behavior if I use Xcode's Master-Detail project template and make a few additions:
added BOOL property 'pinned' to the core data Entity
added Toggle view to the DetailView
added save button to the DetailedView
changed the NSSortDescriptor to use pinned property
It gives me the same unfortunate side effects when I set & save the pinned value to true
an involuntary navigation back to the list view and then again back to the detailed view or
an involuntary navigation to another copy of the same detailed view and then back to the list view.
Fixed in Xcode 12/Beta 4 (maybe even in 3)
Rebooted my MacBook and it solved the issue for me