In the following code I have a List of Cars and each Car from that list has its own list of Services, I can add and delete Cars without a problem by calling carViewModel.addNewCar(make:String, model:String) and carViewModel.deleteCar(at indexSet:IndexSet).
Car.swift
import RealmSwift
final class Car: Object, ObjectKeyIdentifiable{
@objc dynamic var make: String = ""
@objc dynamic var model: String = ""
// creation date, ID etc.
dynamic var services = List<CarService>()
}
CarList.swift
import RealmSwift
final class CarList: Object, ObjectKeyIdentifiable{
@objc dynamic var name: String = ""
// creation date, ID etc.
var cars = RealmSwift.List<Car>()
}
CarService.swift
import RealmSwift
final class CarService: Object, ObjectKeyIdentifiable{
@objc dynamic var serviceName: String = ""
// creation date, ID etc.
}
View Model
import RealmSwift
class CarViewModel: ObservableObject{
@Published var cars = List<Car>()
@Published var selectedCarList: CarList? = nil
var token: NotificationToken? = nil
init(){
// Create a the default lists if they don't already exist.
createDefaultCarList()
createDefaultServiceList()
// Initialize the SelectedCarList and the cars variables items from the Default Car List.
if let list = realm?.objects(CarList.self).first{
self.selectedCarList = list
self.cars = list.cars
}
token = selectedCarList?.observe({ [unowned self] (changes) in
switch changes{
case .error(_): break
case.change(_, _):self.objectWillChange.send()
case.deleted: self.selectedCarList = nil
}
})
}
func addNewCar(make:String, model:String){
if let realm = selectedCarList?.realm{
try? realm.write{
let car = Car()
car.make = make
car.model = model
selectedCarList?.cars.append(car)
}
}
}
func deleteCar(at indexSet:IndexSet){
if let index = indexSet.first,
let realm = cars[index].realm{
try? realm.write{
realm.delete(cars[index])
}
}
}
func addService(toCar: Car, serviceName: String){
try? realm?.write{
let service = CarService()
service.serviceName = serviceName
toCar.services.append(service)
}
}
/// Creates the Default Car List if it doesn't already exists otherwise just prints the error.
func createDefaultCarList(){
do {
if (realm?.objects(CarList.self).first) == nil{
try realm?.write({
let defaultList = CarList()
defaultList.name = "Default Car List"
realm?.add(defaultList)
})
}
}catch let error{
print(error.localizedDescription)
}
}
/// Creates the Default Serivice List if it doesn't already exists otherwise just prints the error.
func createDefaultServiceList(){
do {
if (realm?.objects(ServiceList.self).first) == nil{
try realm?.write({
let defaultList = ServiceList()
defaultList.listName = "Default Service List"
realm?.add(defaultList)
})
}
}catch let error{
print(error.localizedDescription)
}
}
}
My issue is adding or deleting Services to existing Cars. When I call carViewModel.addService(toCar: Car, serviceName: String) I get the error below...
Calling the addService() method.
struct NewServiceFormView: View {
@ObservedObject var carViewModel: CarViewModel
@State var selectedCar:Car // pass from other cars view
var body: some View {
NavigationView {
Form {
// fields
}
.navigationBarItems( trailing:Button("Save", action: addNewCar))
}
}
func addNewCar(){
carViewModel.addService(toCar: selectedCar, serviceName: "Oil Change")
}
}
Error
"Cannot modify managed RLMArray outside of a write transaction."
I can add new Services by explicitly selecting a Car from the cars list. I don't get any errors but the UI doesn't update; I don't see the newly added Service until the app is relaunched.
No errors doing it this way but the UI doesn't update.
carViewModel.addService(toCar: carViewModel.cars[1], serviceName: "Rotors")
How can I properly watch, delete and add Services to existing Cars?
EDIT: Added the following code per Mahan's request.
View to present the NewServiceFormView
struct CarServicesView: View {
@State var selectedCar:Car // a car from parent view
@ObservedObject var carViewModel: CarViewModel
var body: some View {
VStack{
List {
Section(header: Text("Services: \(selectedCar.services.count)")) {
ForEach(selectedCar.services) { service in
}
}
}
.listStyle(GroupedListStyle())
.toolbar {
ToolbarItem(placement: .navigationBarTrailing) {
Button(action: openNewServiceForm) {
Image(systemName: "plus")
}
}
}
}.sheet(isPresented: $newServiceFormIsPresented){
NewServiceFormView(carViewModel: carViewModel, selectedCar: selectedCar)
}
}
func openNewServiceForm() {
newServiceFormIsPresented.toggle()
}
}
