I've noticed several crashes that look like they're caused by an index out of bound in internal methods of NSFetchedResultsController. This happens while changes are merged from the persistent store container into the view context. Here's an example of the last exception backtrace.
Exactly which internal methods that are called in - [NSFetchedResultsController(PrivateMethods) _core_managedObjectContextDidChange:] vary between crash reports but they all end up crashing from _NSArrayRaiseBoundException.
The Core Data stack consists of one persistent store, one persistent store coordinator that the view context is set up to automatically merge changes from, and data is saved to disk from background context.
persistentContainer.loadPersistentStores(...)
viewContext = persistentContainer.viewContext
viewContext.automaticallyMergesChangesFromParent = true
backgroundContext = persistentContainer.newBackgroundContext()
backgroundContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
backgroundClientContext = persistentContainer.newBackgroundContext()
backgroundClientContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
Does anyone have any ideas what could be causing this? Thankful for any ideas or advice on how to investigate further.
Oscar F
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I'm starting with the template code from Apple from:
File > New Project > macOS app using Swift UI and Swift Data. Selection works fine if only adding items, but after deleting any selected item selection stops working for some rows. It seems like the UI and model get out of sync. After restarting the app, or simply launching a new window, it works again. Is this a known bug in Swift UI and is there a workaround?
import SwiftUI
import SwiftData
struct ContentView: View {
@Environment(\.modelContext) private var modelContext
@Query private var items: [Item]
var body: some View {
NavigationSplitView {
List {
ForEach(items) { item in
NavigationLink {
Text("Item at \(item.timestamp, format: Date.FormatStyle(date: .numeric, time: .standard))")
} label: {
Text(item.timestamp, format: Date.FormatStyle(date: .numeric, time: .standard))
}
}
.onDelete(perform: deleteItems)
}
.navigationSplitViewColumnWidth(min: 180, ideal: 200)
.toolbar {
ToolbarItem {
Button(action: addItem) {
Label("Add Item", systemImage: "plus")
}
}
}
} detail: {
Text("Select an item")
}
}
private func addItem() {
withAnimation {
let newItem = Item(timestamp: Date())
modelContext.insert(newItem)
}
}
private func deleteItems(offsets: IndexSet) {
withAnimation {
for index in offsets {
modelContext.delete(items[index])
}
}
}
}
Hi there! I'm really excited about WWDC and the Swift Student Challenge this year!
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