SwiftUI + Core Data - updating an object (Detail -> DetailEdit) - core-data

Question

Goal: update a core data object with SwiftUI: DetailView -> EditDetail -> DetailView (updated).
Problem: code bellow works, but creates a new object, instead of updating existing one.
import SwiftUI
struct DetailView: View {
var order = Order()
#State var showOrderEdit = false
var body: some View {
Form{
Text(order.tableNumber)
Text(order.pizzaType)
}
.navigationTitle(order.pizzaType)
.toolbar {
ToolbarItem(placement: .primaryAction) {
//edit button
Button(action: {
showOrderEdit = true
}, label: {
Text("Edit")
})
.sheet(isPresented: $showOrderEdit) {
OrderEdit(order: order)
}
}
}
}
}
import SwiftUI
struct DetailEdit: View {
#State var tableNumber = ""
#Environment(\.managedObjectContext) private var viewContext
#Environment (\.presentationMode) var presentationMode
var order = Order()
var body: some View {
NavigationView {
Form {
TextField("table number", text: $tableNumber)
//update button
Button(action: {
updateOrder(order: order)
}) {
Text("Update")
.foregroundColor(.blue)
}
}
//passing data item detail -> item edit
.onAppear {
self.tableNumber = self.order.tableNumber
}
.navigationTitle("Edit Order")
}
}
func updateOrder(order: Order) {
let newtableNumber = tableNumber
viewContext.performAndWait {
order.tableNumber = newtableNumber
try? viewContext.save()
}
}

Answer 1

You create new Order object in each view, so it is stored as new one into database. Instead you need to inject CoreData object from parent view (which shows DetailView) as observed object,
struct DetailView: View {
#ObservedObject var order: Order // << here !!
// .. other code
and
struct DetailEdit: View {
#State var tableNumber = ""
#Environment(\.managedObjectContext) private var viewContext
#Environment (\.presentationMode) var presentationMode
#ObservedObject var order: Order // << here !!
// ... other code
in such approach you will work with same instance of Order in both views and they will be updated because observe that instance for modifications.