Value in SwiftUI not being passed - swift

Question

I am trying to pass that a values to let my item know what group it should be added to in Core Data.
Here are some pictures of my App.
Please note that itemsInGroup fetches all of the items that should be in the group.
After adding breakpoints in my app, the value of the group where the Item entity is being add is equal to nil. This should have a value (which is set when the add item button is pressed).
Thank you for your help in advance.
Main part of the code
import SwiftUI
import CoreData
struct ContentView: View {
#Environment(\.managedObjectContext) private var viewContext
enum ActiveSheet: Identifiable {
case first, second
var id: Int {
hashValue
}
}
#FetchRequest(
sortDescriptors: [NSSortDescriptor(keyPath: \Group.timestamp, ascending: true)],
animation: .default)
private var items: FetchedResults<Group>
#State var activeSheet: ActiveSheet?
#State private var selectedGroup: Group? = nil
var body: some View {
NavigationView {
List {
ForEach(items) { group in
// Text("Item at \(item.timestamp!, formatter: itemFormatter)")
Text(group.title ?? "New group")
ForEach(group.itemsInGroup) { item in
Text(item.title ?? "New Item")
}
Button(action: {
selectedGroup = group
activeSheet = .second
}, label: {
Text("Add Item")
})
}
.onDelete(perform: deleteItems)
}
.toolbar {
Button(action: {
activeSheet = .first
}) {
Label("Add Item", systemImage: "plus")
}
}
}
.sheet(item: $activeSheet) { item in
switch(item) {
case .first: AddGroupName()
case .second: AddItemView(group: selectedGroup)
}
}
}
private func addItem() {
withAnimation {
let newItem = Group(context: viewContext)
newItem.timestamp = Date()
do {
try viewContext.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
}
}
private func deleteItems(offsets: IndexSet) {
withAnimation {
offsets.map { items[$0] }.forEach(viewContext.delete)
do {
try viewContext.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
}
}
}
private let itemFormatter: DateFormatter = {
let formatter = DateFormatter()
formatter.dateStyle = .short
formatter.timeStyle = .medium
return formatter
}()
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView().environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
}
}
Where I add a new item
struct AddItemView: View {
#Environment(\.managedObjectContext) private var viewContext
let group: Group?
#State var title = ""
var body: some View {
VStack {
Form {
TextField("Title", text: $title)
Button(action: {
let item = Item(context: viewContext)
item.group = group
item.title = title
try? viewContext.save()
}, label: {
Text("Save")
})
}
}
}
}
Where I add a new group
struct AddGroupName: View {
#Environment(\.managedObjectContext) private var viewContext
#State var title = ""
var body: some View {
VStack {
Form {
TextField("Title", text: $title)
Button(action: {
let item = Group(context: viewContext)
item.title = title
item.timestamp = Date()
try? viewContext.save()
}, label: {
Text("Save")
})
}
}
}
}
My Core Data Model
Why is the group value not being passed and saved correctly? It should be saved in the selectedGroup variable in the main part of the code.
When I try and add an item and save it to the core data database I get this error "Illegal attempt to establish a relationship 'group' between objects in different contexts"
Please note that I have tried setting selectedGroup equal to a value other than nil, but then this initial value is used when trying to add an item.

Answer 1

You should declare your group property using the #Binding property wrapper in AddItemView
#Binding var group: Group
This way the #State property selectedGroup will be updated when the AddItemView is dismissed