How to completely delete items when using #ObservedResults in Realm and SwiftUI - swiftui

Question

I'm trying the new Realm 10 wrappers by using the example given in the Realm documentation Integration Guides -> SwiftUI & Combine and I like how simple it is to add and delete records when using the #ObservedResults and the #ObservedRealmObject. The one thing I don't quite understand is why when deleting items from the Group object it only removes the items from the Group but leaves the actual items in the Item Realm object undeleted. See the Realm Browser image below.
Here is what the Realm Browser shows after adding and deleting four (4) items through the app UI, as you can see the four (4) items were deleted from the Group but left all four (4) items in the Item object.
Can someone please explain why the items don't get deleted from the Item object only from the Group object when calling .onDelete(perform: $group.items.remove)? How can I delete them?
I tried deleting them like this...
ItemsView.swift
.onDelete(perform: deleteItems)
func deleteItems(at offsets: IndexSet){
let realm = try? Realm()
try! realm?.write {
// 1. delete items
for item in list.items{
realm?.delete(item)
}
// 2. delete the list
realm?.delete(list)
}
}
but I got the following error:
Thread 1: "Can only delete an object from the Realm it belongs to."
Again, the whole code can be found in the Integration Guides - Without Sync.
EDIT: Added code for, LocalOnlyContentView, ItemsView, Group and Item models.
Item.swift
import Foundation
import RealmSwift
/// Random adjectives for more interesting demo item names
let randomAdjectives = [
"fluffy", "classy", "bumpy", "bizarre", "wiggly", "quick", "sudden",
"acoustic", "smiling", "dispensable", "foreign", "shaky", "purple", "keen",
"aberrant", "disastrous", "vague", "squealing", "ad hoc", "sweet"
]
/// Random noun for more interesting demo item names
let randomNouns = [
"floor", "monitor", "hair tie", "puddle", "hair brush", "bread",
"cinder block", "glass", "ring", "twister", "coasters", "fridge",
"toe ring", "bracelet", "cabinet", "nail file", "plate", "lace",
"cork", "mouse pad"
]
final class Item: Object, ObjectKeyIdentifiable {
#Persisted(primaryKey: true) var _id: ObjectId
#Persisted var name = "\(randomAdjectives.randomElement()!) \(randomNouns.randomElement()!)"
#Persisted var isFavorite = false
#Persisted(originProperty: "items") var group: LinkingObjects<Group>
}
Group.swift
import Foundation
import RealmSwift
final class Group: Object, ObjectKeyIdentifiable {
#Persisted(primaryKey: true) var _id: ObjectId
#Persisted var items = RealmSwift.List<Item>()
}
ItemsView.swift
struct ItemsView: View {
#ObservedRealmObject var group: Group
var leadingBarButton: AnyView?
var body: some View {
NavigationView {
VStack {
// The list shows the items in the realm.
List {
ForEach(group.items) { item in
ItemRow(item: item)
}
.onDelete(perform: $group.items.remove)
.onMove(perform: $group.items.move)
}.listStyle(GroupedListStyle())
.navigationBarTitle("Items", displayMode: .large)
.navigationBarBackButtonHidden(true)
.navigationBarItems(
leading: self.leadingBarButton,
trailing: EditButton())
HStack {
Spacer()
Button(action: {
$group.items.append(Item())
}) { Image(systemName: "plus") }
}.padding()
}
}
}
}
LocalOnlyContentView.swift
struct LocalOnlyContentView: View {
#ObservedResults(Group.self) var groups
var body: some View {
if let group = groups.first {
AnyView(ItemsView(group: group))
} else {
AnyView(ProgressView().onAppear {
$groups.append(Group())
})
}
}
}
SceneDelegate.swift
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
let contentView = LocalOnlyContentView()
if let windowScene = scene as? UIWindowScene {
let window = UIWindow(windowScene: windowScene)
window.rootViewController = UIHostingController(rootView: contentView)
self.window = window
window.makeKeyAndVisible()
}
}

Answer 1

Keep in mind that what's being shown in that tutorial is how to remove an item from a group's List - not how to totally delete the item.
Going very high level with this answer - objects in a List are not the actual objects - they are a "pointer" to the actual item stored on disk.
Suppose you have three items
Item 0
Item 1
Item 2
and a Group with List of items
MyGroup
List of items
Item 0
Item 1
Item 2
What's actually going on is the List "points" to the items on disk
My Group
List of items
pointer to Item 0
pointer to Item 1
pointer to Item 2
So when this is called $group.items.remove it's removing the pointer to the item from the list, not the item itself.
The solution (well, one of the solutions) is to remove the actual item
let myItemToRemove = List of items[0] //get the item at index 0
realm.remove(myItemToRemove) // removes the item itself from realm, along
// with the pointer stored in the list
The code to actually delete an item is this
try? realm.write {
realm.delete(objectToDelete)
}