Crash when deleting data with relation in RealmSwift - swift

Question

I am creating an application using RealmSwift.
The following implementation crashed when deleting related data.
After removing only "UnderlayerItem", it succeeded.
Crash when deleting UnderlayerItem and deleting Item.
The error is:
Thread 1: Exception: "The RLMArray has been invalidated or the object
containing it has been deleted."
How do I delete without crashing?
struct ListView: View {
#ObservedObject private var fetcher = Fetcher()
#State private var title = ""
var body: some View {
NavigationView {
VStack {
TextField("add", text: $title) {
let item = Item()
item.title = self.title
let realm = try! Realm()
try! realm.write {
realm.add(item)
}
self.title = ""
}
ForEach(self.fetcher.items) { (item: Item) in
NavigationLink(destination: DetailView(item: item, id: item.id)) {
Text(item.title)
}
}
}
}
}
}
struct DetailView: View {
var item: Item
var id: String
#State private var title = ""
#ObservedObject private var fetcher = Fetcher()
#Environment(\.presentationMode) private var presentationMode: Binding<PresentationMode>
var body: some View {
VStack {
TextField("add", text: $title) {
let realm = try! Realm()
if let item = realm.objects(Item.self).filter("id == '\(self.id)'").first {
try! realm.write() {
let underlayerItem = UnderlayerItem()
underlayerItem.title = self.title
item.underlayerItems.append(underlayerItem)
}
}
self.title = ""
}
ForEach(self.item.underlayerItems) { (underlayerItems: UnderlayerItem) in
Text(underlayerItems.title)
}
Button(action: {
self.presentationMode.wrappedValue.dismiss()
self.fetcher.delete(id: self.id)
}) {
Text("Delete")
}
}
}
}
class Fetcher: ObservableObject {
var realm = try! Realm()
var objectWillChange: ObservableObjectPublisher = .init()
private(set) var items: Results<Item>
private var notificationTokens: [NotificationToken] = []
init() {
items = realm.objects(Item.self)
notificationTokens.append(items.observe { _ in
self.objectWillChange.send()
})
}
func delete(id: String) {
guard let item = realm.objects(Item.self).filter("id == '\(id)'").first else { return }
try! realm.write() {
for underlayerItem in item.underlayerItems {
realm.delete(realm.objects(UnderlayerItem.self).filter("id == '\(underlayerItem.id)'").first!)
}
}
try! realm.write() {
realm.delete(item)
}
}
}
class Item: Object, Identifiable {
#objc dynamic var id = NSUUID().uuidString
#objc dynamic var title = ""
#objc dynamic var createdAt = NSDate()
let underlayerItems: List<UnderlayerItem> = List<UnderlayerItem>()
override static func primaryKey() -> String? {
return "id"
}
}
class UnderlayerItem: Object, Identifiable {
#objc dynamic var id = NSUUID().uuidString
#objc dynamic var title = ""
#objc dynamic var createdAt = NSDate()
override static func primaryKey() -> String? {
return "id"
}
}

Answer 1

You don't need to iterate over the objects in the list to delete them. Just do this
try! realm.write() {
realm.delete(item.underlayerItems)
}
I believe it's crashing because you're attempting to access an item that was deleted
self.item.underlayerItems