Edit details of a dynamic list of core data object - swift

Question

I used the Xcode default CoreData template to build my app.
I have tried to use CoreData and create an entity like this:
I then created a AddItemView which allows me to add item to the view.
struct AddItemView: View {
#Environment(\.managedObjectContext) var viewContext
#Environment(\.presentationMode) var presentationMode
#State private var notes = ""
#State private var selectedDate = Date()
var body: some View {
NavigationView {
Form {
Section {
TextField("notes", text: $notes)
}
Section {
DatePicker("", selection: $selectedDate, displayedComponents: .date)
Text("Your selected date: \(selectedDate)")
}
Section {
Button("Save") {
let newItem = Item(context: self.viewContext)
newItem.notes = self.notes
newItem.recordDate = self.selectedDate
newItem.timestamp = Date()
try? self.viewContext.save()
self.presentationMode.wrappedValue.dismiss()
}
}
}
.navigationBarTitle("Add Item")
}
}
}
It works well and can add items.
Then I want to click on each of the item to go to a Detail View. In the DetailView, there should be an edit button to allow me to modify the object.
I therefore created three files for the purpose: ItemHost, DetailView, EditorView
The Navigation Destination of the item will go to the ItemHost.
struct ItemListView: View {
#Environment(\.managedObjectContext) private var viewContext
#FetchRequest(
sortDescriptors: [NSSortDescriptor(keyPath: \Item.timestamp, ascending: true)],
animation: .default)
private var items: FetchedResults<Item>
#State private var showingAddScreen = false
var body: some View {
NavigationView {
List {
ForEach(items, id: \.self) { item in
NavigationLink(destination: ItemHost(item: item)) {
VStack {
Text("Item at \(item.timestamp!, formatter: FormatterUtility.dateTimeFormatter)")
Text("notes: \(item.notes ?? "")")
Text("Item Date: \(item.recordDate!, formatter: FormatterUtility.dateFormatter)")
}
}
}
.onDelete(perform: deleteItems)
}
.toolbar {
ToolbarItem(placement: .navigationBarLeading) {
#if os(iOS)
EditButton()
#endif
}
ToolbarItem(placement: .navigationBarTrailing) {
Button(action: {self.showingAddScreen.toggle()}) {
Label("Add Item", systemImage: "plus")
}
}
}
.sheet(isPresented: $showingAddScreen) {
AddItemView().environment(\.managedObjectContext, self.viewContext)
}
}
}
The ItemHost as follows:
struct ItemHost: View {
#Environment(\.editMode) var editMode
#Environment(\.managedObjectContext) var contextView
#State var item: Item
var body: some View {
NavigationView {
if editMode?.wrappedValue == .active {
Button("Cancel") {
editMode?.animation().wrappedValue = .inactive
}
}
if editMode?.wrappedValue == .inactive {
ItemDetailView(item: item)
} else {
ItemEditor(item: item)
}
}.navigationBarTitle("EditMode Problem")
.navigationBarItems(trailing: EditButton())
}
}
The DetailView is just a view to display the details, without any special.
struct ItemDetailView: View {
#Environment(\.managedObjectContext) var contextView
#Environment(\.presentationMode) var presentationMode
#State private var showingDeleteAlert = false
let item: Item
var body: some View {
VStack {
Text("notes: \(item.notes ?? "")")
Text("Record Date: \(item.recordDate!, formatter: FormatterUtility.dateFormatter)")
}
.navigationBarTitle(Text("Item Detail"), displayMode: .inline)
.alert(isPresented: $showingDeleteAlert) {
Alert(title: Text("Delete Item"), message: Text("Are you sure?"),
primaryButton: .destructive(Text("Delete")) {
self.deleteItem()
}, secondaryButton: .cancel()
)
}
.navigationBarItems(trailing: Button(action: {
self.showingDeleteAlert = true
}) {
Image(systemName: "trash")
})
}
// Problem here
// Can delete the item and go back to list page. But the actual item in the CoreData has not been removed. If I call contextView.save() it will crash.
func deleteItem() {
contextView.delete(item)
presentationMode.wrappedValue.dismiss()
}
}
The EditorView like this:
struct ItemEditor: View {
#Environment(\.presentationMode) var presentation
#State var item: Item
var body: some View {
List {
HStack {
Text("Notes").bold()
TextField("Notes", text: $item.notes) // Error
}
// Error
DatePicker(selection: $item.recordDate, displayedComponents: .date) {
Text("Record Date").bold()
}
}
}
}
A few problem here:
ItemEditor: Cannot convert value of type 'Binding<String?>' to expected argument type 'Binding'. I have no way to pick the original item object values and display it to let the user know what was the old value inside the object.
Nothing to be displayed once I click on the individual navigation item. I expect that it will originally (not edit mode) and then show the detail view. If it is edit mode, then show the editor.
I get confused with the #binding and how to pass the item into the DetailView and also the Editor. How the editor save the data back to the item object in the contextView?
For the deleteItem() in the ItemDetailView. It can remove the item and go back to the ItemListView apparently. However, when I quit the app, and then run again. I found that the item re-appeared again, not really deleted.
Click on the item now, it shows this:

Answer 1

Don't use #State to var Item in Core Data. You should use #ObservedObject instead. It will refresh a parent view after updating data.
Please read this article:
https://purple.telstra.com/blog/swiftui---state-vs--stateobject-vs--observedobject-vs--environme