iOS OSX max

Mutating Core Data object

Problem: How to mutate a fetched CD object in child views


import SwiftUI import CoreData struct ContentView: View { @Environment(\.managedObjectContext) private var viewContext @FetchRequest( sortDescriptors: [NSSortDescriptor(keyPath: \Item.timestamp, ascending: true)], animation: .default) var items: FetchedResults<Item> var body: some View { NavigationView { List { ForEach(items) { item in NavigationLink { ItemDetail(item: item) } label: { Text("itemview1 at \(item.timestamp!, formatter: itemFormatter) name: \((item.name ?? "").isEmpty ? "": item.name! )") } } .onDelete(perform: deleteItems) } .toolbar { #if os(iOS) ToolbarItem(placement: .navigationBarTrailing) { EditButton() } #endif ToolbarItem { Button(action: addItem) { Label("Add Item", systemImage: "plus") } } } Text("Select an item") } } private func addItem() { withAnimation { let newItem = Item(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 ItemDetail: View { @ObservedObject var item: Item @State var name: String = "" var body: some View { Form { TextField("Enter name", text: $name ).onChange(of: name) { newValue in item.name = name } Button("Submit") { // nav back } Spacer() NavigationLink { ItemDetail(item: item) } label: { Text("itemview1 at \(item.timestamp!, formatter: itemFormatter) name: \((item.name ?? "").isEmpty ? "": item.name! )") } } } } struct ContentView_Previews: PreviewProvider { static var previews: some View { ContentView().environment(\.managedObjectContext, PersistenceController.preview.container.viewContext) } }

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