CoreData and SwiftUI - swift

Question

hello i'm try to implement Core Data and swiftUI for my project.
I created an Entity called Aeroporti, which contain 2 attributes iataAPT : String and icaoAPT: string.
I want to save simple data on that.
I setup the app delegate like this:
// MARK: - Core Data stack
lazy var persistentContainer: NSPersistentContainer = {
let container = NSPersistentContainer(name: "testFirebaseCoreData")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
// MARK: - Core Data Saving support
func saveContext () {
let context = persistentContainer.viewContext
if context.hasChanges {
do {
try context.save()
} catch {
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
my content view list the field icaoAPT in the entity Aeroporti
import SwiftUI
import CoreData
struct ContentView: View {
#ObservedObject var dm : DataManager
#Environment(\.managedObjectContext) var managedObjectContext
#FetchRequest(entity: Aeroporti.entity(),
sortDescriptors: [NSSortDescriptor(keyPath: \Aeroporti.icaoAPT, ascending: true)]) var aeroport : FetchedResults<Aeroporti> // crea la variabile che contiene le ricette
var body: some View {
List{
HStack{
// NOT WORKING IF USING DataMANAGER
// Button(action: {
// self.dm.provaSalva()
// }) {
// Text("save from manager")
// }
saveFromView // button save from view
}
ForEach(aeroport, id: \.self) { apt in
Text(apt.icaoAPT ?? "sconosciuto")
// .environment(\.managedObjectContext, self.managedObjectContext)
}
}
}
var saveFromView : some View {
Button(action: {
let apt = Aeroporti(context: self.managedObjectContext)
apt.iataAPT = "MFM"
apt.icaoAPT = "VMMC"
do {
try self.managedObjectContext.save()
print("airport saved.")
} catch {
print(error.localizedDescription)
}
}) {
Text("save fromview")
}
}
}
all working fine and the data is saved if I use the button (saveFromView) in the ContentView.
now, in order to better handle the data I have create a DataManager where I put the same code to save the data in the entity, and I try to lunch this code on the content view via a button (save from manager) but it doest work, i'm getting the error "The operation couldn’t be completed. (Foundation._GenericObjCError error 0.)" when it save.
import Combine
import SwiftUI
import CoreData
class DataManager: ObservableObject {
let objectWillChange = PassthroughSubject<Void, Never>()
#Environment(\.managedObjectContext) var managedObjectContext
func provaSalva() {
let apt = Aeroporti(context: managedObjectContext)
apt.iataAPT = "MFM"
apt.icaoAPT = "VMMC"
do {
try self.managedObjectContext.save()
print("airport saved.")
} catch {
print(error.localizedDescription)
}
}
}
the question is?? why.. is the same code... how can I solve this issue if I want to handle the save data not in the ContentView.
thanks for the help..

Answer 1

Give this a try. This is the implementation I use for my app.
class DataManager {
//MARK: - Setup
//Singleton object
static let defaults = DataManager()
private init() {}
//Managed object context
var moc: NSManagedObjectContext {
return (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
}
//Save context, if changes were made
func save() {
if moc.hasChanges {
do {
print("Sucess!!")
try moc.save()
} catch {
print("Error while saving managedObjectContext \(error)")
}
}
}
//MARK: - Insert
//What you want to save
func provaSalva() {
let apt = Aeroporti(context: moc)
apt.iataAPT = "MFM"
apt.icaoAPT = "VMMC"
save()
}
}
Your saveFromView:
var saveFromView : some View {
Button(action: {
DataManager.defaults.provaSalva()
}) {
Text("save fromview")
}
}

Answer 2

solved by passing the db to the function
func provaSalva(dbCore: NSManagedObjectContext) {
let apt = Aeroporti(context: dbCore)
apt.iataAPT = "MFM"
apt.icaoAPT = "VMMC"
do {
try dbCore.save()
print("airport saved.")
} catch {
print(error.localizedDescription)
}
}