I just cannot figure out how to pass core data values of an item from ForEach list in NavigationLink to Detail view. Here is the code that got error: "Cannot convert value of type 'FetchedResults.Element' (aka 'FileEnt') to expected argument type 'FileViewModel'"
struct FileList: View {
#Environment(\.managedObjectContext) var context
#FetchRequest(entity: FileEnt.entity(), sortDescriptors: [NSSortDescriptor(key: "fileName", ascending: false)]) var results: FetchedResults<FileEnt>
#ObservedObject var fileData : FileViewModel
var body: some View {
NavigationView {
List {
ForEach(results) { aFile in
NavigationLink(destination: FileDetails(fileData: aFile), label: {
// ** error on red-underscored aFile above.
Text(aFile.fileName ?? "")
})
}
}.navigationBarTitle("Files")
}
}
}
FileViewModel is for Add, Edit and Detail views. Here is its simplified version for the question:
class FileViewModel: ObservableObject {
#Published var fileName = ""
init(){
}
func DetailItem(fileItem: FileEnt){
fileName = fileItem.fileName ?? ""
}
}
FileDetails:
struct FileDetails: View {
#ObservedObject var fileData : FileViewModel
#Environment(\.managedObjectContext) var context
#State var isEdit = false
var body: some View {
VStack {
Form {
HStack {
Text("File Name:")
Spacer()
Text(fileData.fileName)
....
Modified the post for easy understanding. Thanks for any advice.
Related
G'day everyone,
I'm trying to work out how CoreData relationships can work with UI elements like pickers.
At the moment I have a 3 view app (based on the Xcode boilerplate code) which displays a list of parent entities, which have children which have children. I want a picker to select which grandchild a child entity should refer to.
At the moment I have two funny side effects:
When I run the app as a preview (so there is pre-populated data... this sample code will break without the data in place),
the selected grandchild in the picker is the grandchild of the first
child, irrespective of which child you're dropped into in the first
view.
When I drop back and pick another child, now the picked grabs the correct initial selection from the child entity
When I select a child and "save" that, the value in the child summary does not change, until I click another child at which point the value changes before the transition to the modal view.
I am clearly missing something in my understanding of the sequence of events when presenting modals in SwiftUI... can any what shed any light on what I've done wrong?
Here's a video to make this more clear:
https://github.com/andrewjdavison/Test31/blob/main/Test31%20-%20first%20click%20issue.mov?raw=true
Git repository of the sample is https://github.com/andrewjdavison/Test31.git, but in summary:
Data Model:
View Source:
import SwiftUI
import CoreData
struct LicenceView : View {
#Environment(\.managedObjectContext) private var viewContext
#Binding var licence: Licence
#Binding var showModal: Bool
#State var selectedElement: Element
#FetchRequest private var elements: FetchedResults<Element>
init(currentLicence: Binding<Licence>, showModal: Binding<Bool>, context: NSManagedObjectContext) {
self._licence = currentLicence
self._showModal = showModal
let fetchRequest: NSFetchRequest<Element> = Element.fetchRequest()
fetchRequest.sortDescriptors = []
self._elements = FetchRequest(fetchRequest: fetchRequest)
_selectedElement = State(initialValue: currentLicence.wrappedValue.licenced!)
}
func save() {
licence.licenced = selectedElement
try! viewContext.save()
showModal = false
}
var body: some View {
VStack {
Button(action: {showModal = false}) {
Text("Close")
}
Picker(selection: $selectedElement, label: Text("Element")) {
ForEach(elements, id: \.self) { element in
Text("\(element.desc!)")
}
}
Text("Selected: \(selectedElement.desc!)")
Button(action: {save()}) {
Text("Save")
}
}
}
}
struct RegisterView : View {
#Environment(\.managedObjectContext) private var viewContext
#State var showModal: Bool = false
var currentRegister: Register
#State var currentLicence: Licence
init(currentRegister: Register) {
currentLicence = Array(currentRegister.licencedUsers! as! Set<Licence>)[0]
self.currentRegister = currentRegister
}
var body: some View {
VStack {
List {
ForEach (Array(currentRegister.licencedUsers! as! Set<Licence>), id: \.self) { licence in
Button(action: {currentLicence = licence; showModal = true}) {
HStack {
Text("\(licence.leasee!) : ")
Text("\(licence.licenced!.desc!)")
}
}
}
}
}
.sheet(isPresented: $showModal) {
LicenceView(currentLicence: $currentLicence, showModal: $showModal, context: viewContext )
}
}
}
struct ContentView: View {
#Environment(\.managedObjectContext) private var viewContext
#FetchRequest(
sortDescriptors: [NSSortDescriptor(keyPath: \Register.id, ascending: true)],
animation: .default)
private var registers: FetchedResults<Register>
var body: some View {
NavigationView {
List {
ForEach(registers) { register in
NavigationLink(destination: RegisterView(currentRegister: register)) {
Text("Register id \(register.id!)")
}
}
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView().environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
}
}
[1]: https://i.stack.imgur.com/AfaNb.png
I didn't really understand this
• selected grandchild in the picker is the grandchild of the first child, irrespective of which child you're dropped into in the first view.
• When I drop back and pick another child, now the picked grabs the correct initial selection from the child entity
Could you attach a video that represents a problem?
But I can give you a solution to the preview problem and the second one.
Preview
If you use preview with Core Data, you need to use a viewContextcreated with MockData and pass it to your View. Here I provide a generic code, that can be modified for each of your views:
In your Persistance struct (CoreData Manager) declare a variable preview with your preview Items:
static var preview: PersistenceController = {
let result = PersistenceController(inMemory: true)
let viewContext = result.container.viewContext
// Here you create your Mock Data
let newItem = Item(context: viewContext)
newItem.yourProperty = yourValue
do {
try viewContext.save()
} catch {
// error handling
}
return result
}()
Make sure it has inMemory: Bool in its init, as it is responsible for separating real viewContext and previewContext:
init(inMemory: Bool = false) {
container = NSPersistentContainer(name: "TestCD")
if inMemory {
container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
}
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
}
Create Mock Item from your viewContext and pass it to preview:
struct YourView_Previews: PreviewProvider {
static var previews: some View {
let context = PersistenceController.preview.container.viewContext
let request: NSFetchRequest<Item> = Item.fetchRequest()
let fetchedItems = try! context.fetch(request)
YourView(item: fetchedItems)
}
}
If you use #FetchRequest and #FetchedResults it makes it easier, as they will do creating and fetching objects for you. Just implement a preview like this:
struct YourView_Previews: PreviewProvider {
static var previews: some View {
YourView().environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
}
}
Here is Persistence struct created by Xcode at the moment of the project initialization:
import CoreData
struct PersistenceController {
static let shared = PersistenceController()
static var preview: PersistenceController = {
let result = PersistenceController(inMemory: true)
let viewContext = result.container.viewContext
let item = Item(context: viewContext)
item.property = yourProperty
do {
try viewContext.save()
} catch {
}
return result
}()
let container: NSPersistentContainer
init(inMemory: Bool = false) {
container = NSPersistentContainer(name: "TestCD")
if inMemory {
container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
}
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
}
}
Second problem
Core Data objects are built with classes, so their type is a reference. When you change a property is a class it doesn't notifiy the view struct to redraw with a new value. (exception is classes, that are created to notify about changes.)
You need to explicitly tell your RegisterView struct to redraw itself after you dismiss your LicenceView. You can do it by creating one more variable in your RegisterView - #State var id = UUID(). Then attach an .id(id) modifier at the end of your VStack
VStack {
//your code
}.id(id)
Finally, create a function viewDismissed which will change the id property in your struct:
func viewDismissed() {
id = UUID()
}
Now, attach this function to your sheet with an optional parameter onDismiss
.sheet(isPresented: $showModal, onDismiss: viewDismissed) {
LicenceView(currentLicence: $currentLicence, showModal: $showModal, context: viewContext )
}
OK. Huge vote of thanks to Lorem for getting me to the answer. Thanks too for Roma, but it does turn out that his solution, whilst it worked to resolve one of my key problems, does introduce inefficiencies - and didn't resolve the second one.
If others are hitting the same issue I'll leave the Github repo up, but the crux of it all was that #State shouldn't be used when you're sharing CoreData objects around. #ObservedObject is the way to go here.
So the resolution to the problems I encountered were:
Use #ObservedObject instead of #State for passing around the CoreData objects
Make sure that the picker has a tag defined. The documentation I head read implied that this gets generated automatically if you use ".self" as the id for the objects in ForEach, but it seems this is not always reliable. so adding ".tag(element as Element?)" to my picker helped here.
Note: It needed to be an optional type because CoreData makes all the attribute types optional.
Those two alone fixed the problems.
The revised "LicenceView" struct is here, but the whole solution is in the repo.
Cheers!
struct LicenceView : View {
#Environment(\.managedObjectContext) private var viewContext
#ObservedObject var licence: Licence
#Binding var showModal: Bool
#FetchRequest(
sortDescriptors: [NSSortDescriptor(keyPath: \Element.desc, ascending: true)],
animation: .default)
private var elements: FetchedResults<Element>
func save() {
try! viewContext.save()
showModal = false
}
var body: some View {
VStack {
Button(action: {showModal = false}) {
Text("Close")
}
Picker(selection: $licence.licenced, label: Text("Element")) {
ForEach(elements, id: \.self) { element in
Text("\(element.desc!)")
.tag(element as Element?)
}
}
Text("Selected: \(licence.licenced!.desc!)")
Button(action: {save()}) {
Text("Save")
}
}
}
}
I cannot figure out how to tie in the #State var to a picker so that #FetchRequest will update.
This code compiles, but changing the picker selection does nothing to fetchRequest, because it's not calling the init. All kinds of other variants have failed mostly.
How do I accomplish this?
struct ContentView: View {
#Environment(\.managedObjectContext) private var viewContext
#State private var selectedSkill: Skill? = nil
#State private var pickerSelection: Int
#FetchRequest var skills: FetchedResults<Skill>
init(pickerSelection: Int) {
self._pickerSelection = State(initialValue: pickerSelection)
self._skills = FetchRequest(
entity: Skill.entity(),
sortDescriptors: [NSSortDescriptor(keyPath: \Skill.value, ascending: true)],
predicate: NSPredicate(format: "apparatus == %d", pickerSelection)
)
}
There are a few ways to go about this here is mine. Not sure of your intended use of Skill but I think you can figure out how to make it work for you.
I would make apparatus an enum
enum Apparatus: Int, CaseIterable, CustomStringConvertible, Identifiable {
case vault, unevenBars, balanceBeam, all
var id: String { self.description }
var description: String {
switch self {
case .vault: return "Vault"
case .unevenBars: return "Uneven Bars"
case .balanceBeam: return "Balance Beam"
case .all: return "All"
}
}
}
extend on Item
extension Item {
var unwrappedApparatus: Apparatus {
Apparatus(rawValue: Int(apparatus)) ?? Apparatus.vault
}
var unwrappedName: String {
name ?? "Unknown"
}
}
Set your #State in ContentView
struct ContentView: View {
#Environment(\.managedObjectContext) private var viewContext
#State var selectedApparatus = Apparatus.vault
var body: some View {
List {
Picker("Apparatus", selection: $selectedApparatus) {
Text("Vault").tag(Apparatus.vault)
Text("Uneven Bars").tag(Apparatus.unevenBars)
Text("Balance Beam").tag(Apparatus.balanceBeam)
Text("All").tag(Apparatus.all)
}
Text(selectedApparatus.description)
ItemsView(selectedApparatus: $selectedApparatus) // <-- View changing on selectedApparatus
}
}
}
Now break out the View you want to change based on the selectedApparatus to its own View
struct ItemsView: View {
#FetchRequest private var items: FetchedResults<Item>
init(selectedApparatus: Binding<Apparatus>) {
self._items = FetchRequest(entity: Item.entity(),
sortDescriptors: [NSSortDescriptor(keyPath: \Item.name, ascending: true)],
predicate: selectedApparatus.wrappedValue == .all ? nil : NSPredicate(format: "apparatus == %d", selectedApparatus.wrappedValue.rawValue))
}
var body: some View {
ForEach(items) { item in
Text(item.unwrappedName)
}
}
}
Using SwiftUI
I have created a CoreData Entity called SystemSettings and would like to use the information stored in it for calculating results in different functions on different views without using ForEach. SystemSettings will always have only one object (Record) stored from preloaded database. Is there a way I can use #FetchRequest and pull out the only object and its attributes out, as a var.... ?
Thank you
import SwiftUI
import CoreData
struct NewComponent: View {
#FetchRequest(entity: SystemSettings.entity(), sortDescriptors: []) var settings: FetchedResults<SystemSettings>
#Environment(\.managedObjectContext) var moc
#Environment(\.presentationMode) var presentationMode
var calculator = Calculator()
// USER DATA TEXT FIELDS
#State var parameterOne = "12.5"
#State var parameterTwo = "2.5"
#State var calculationResult = ""
var body: some View {
VStack {
Form {
Section (header: Text("Parameters").font(.headline).bold().italic()) {
HStack {
Text ("Length")
.font(.headline)
Spacer()
TextField ("m", text: $parameterOne).modifier(ClearButton(text: $parameterOne))
.multilineTextAlignment(.trailing)
.keyboardType(.decimalPad)
.font(.headline)
}
HStack {
Text ("Width")
.font(.headline)
Spacer()
TextField ("m", text: $parameterTwo).modifier(ClearButton(text: $parameterTwo))
.multilineTextAlignment(.trailing)
.keyboardType(.decimalPad)
.font(.headline)
}
}
}
Section(header:
Text("\(self.calculationResult)").bold().italic().padding(.top)
) {
Button(action: {
self.calculationResult = self.result()
}) {
HStack {
Spacer()
Image(systemName: "x.squareroot")
Text("Calculate!")
Spacer()
}.font(.headline).foregroundColor(Color.green)
.padding(.bottom, 40.0).padding(.top, 20.0)
}
}
}.navigationBarTitle(Text("Component Calculator"))
.gesture(DragGesture().onChanged{_ in UIApplication.shared.sendAction(#selector(UIResponder.resignFirstResponder), to: nil, from: nil, for: nil)})
.modifier(KeyboardObserving())
.navigationBarItems(trailing: Button(action: {
let newEstimatedComponent = EstimatedComponents(context: self.moc)
newEstimatedComponent.name = "New Component"
newEstimatedComponent.price = self.priceToDisplay()
try? self.moc.save()
self.presentationMode.wrappedValue.dismiss()
}){Image(systemName: "checkmark.circle").font(.system(size: 30))})
}
func result () -> String {
let result = componentCost()
return (String(format: "%.2f",(result)) + " €")
}
func priceToDisplay() -> Double {
return componentCost()
}
func componentCost () -> Double {
return calculator (componentWidth: Double(parameterOne), componentHight: Double(parameterTwo), componentPrice: settings!.componentM2Price )
}
/*settings!componentM2Price not working of course, so I need to get the first and the only object from SystemSettings Entity in a way that I can use it in func componentCost()...*/
THANKS AGAIN...
Solved!
#EnvironmentObject var settings: ModifySystemSettings
let systemSettings: SystemSettings
You can find more information here:
https://www.hackingwithswift.com/quick-start/swiftui/how-to-use-environmentobject-to-share-data-between-views
In a SwiftUI View i have a List based on #FetchRequest showing data of a Primary entity and the via relationship connected Secondary entity.
The View and its List is updated correctly, when I add a new Primary entity with a new related secondary entity.
The problem is, when I update the connected Secondary item in a detail view, the database gets updated, but the changes are not reflected in the Primary List.
Obviously, the #FetchRequest does not get triggered by the changes in another View.
When I add a new item in the primary view thereafter, the previously changed item gets finally updated.
As a workaround, i additionally update an attribute of the Primary entity in the detail view and the changes propagate correctly to the Primary View.
My question is:
How can I force an update on all related #FetchRequests in SwiftUI Core Data?
Especially, when I have no direct access to the related entities/#Fetchrequests?
import SwiftUI
extension Primary: Identifiable {}
// Primary View
struct PrimaryListView: View {
#Environment(\.managedObjectContext) var context
#FetchRequest(
entity: Primary.entity(),
sortDescriptors: [NSSortDescriptor(key: "primaryName", ascending: true)]
)
var fetchedResults: FetchedResults<Primary>
var body: some View {
List {
ForEach(fetchedResults) { primary in
NavigationLink(destination: SecondaryView(primary: primary)) {
VStack(alignment: .leading) {
Text("\(primary.primaryName ?? "nil")")
Text("\(primary.secondary?.secondaryName ?? "nil")").font(.footnote).foregroundColor(.secondary)
}
}
}
}
.navigationBarTitle("Primary List")
.navigationBarItems(trailing:
Button(action: {self.addNewPrimary()} ) {
Image(systemName: "plus")
}
)
}
private func addNewPrimary() {
let newPrimary = Primary(context: context)
newPrimary.primaryName = "Primary created at \(Date())"
let newSecondary = Secondary(context: context)
newSecondary.secondaryName = "Secondary built at \(Date())"
newPrimary.secondary = newSecondary
try? context.save()
}
}
struct PrimaryListView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
return NavigationView {
PrimaryListView().environment(\.managedObjectContext, context)
}
}
}
// Detail View
struct SecondaryView: View {
#Environment(\.presentationMode) var presentationMode
var primary: Primary
#State private var newSecondaryName = ""
var body: some View {
VStack {
TextField("Secondary name:", text: $newSecondaryName)
.textFieldStyle(RoundedBorderTextFieldStyle())
.padding()
.onAppear {self.newSecondaryName = self.primary.secondary?.secondaryName ?? "no name"}
Button(action: {self.saveChanges()}) {
Text("Save")
}
.padding()
}
}
private func saveChanges() {
primary.secondary?.secondaryName = newSecondaryName
// TODO: ❌ workaround to trigger update on primary #FetchRequest
primary.managedObjectContext.refresh(primary, mergeChanges: true)
// primary.primaryName = primary.primaryName
try? primary.managedObjectContext?.save()
presentationMode.wrappedValue.dismiss()
}
}
I also struggled with this and found a very nice and clean solution:
You have to wrap the row in a separate view and use #ObservedObject in that row view on the entity.
Here's my code:
WineList:
struct WineList: View {
#FetchRequest(entity: Wine.entity(), sortDescriptors: [
NSSortDescriptor(keyPath: \Wine.name, ascending: true)
]
) var wines: FetchedResults<Wine>
var body: some View {
List(wines, id: \.id) { wine in
NavigationLink(destination: WineDetail(wine: wine)) {
WineRow(wine: wine)
}
}
.navigationBarTitle("Wines")
}
}
WineRow:
struct WineRow: View {
#ObservedObject var wine: Wine // !! #ObserveObject is the key!!!
var body: some View {
HStack {
Text(wine.name ?? "")
Spacer()
}
}
}
You need a Publisher which would generate event about changes in context and some state variable in primary view to force view rebuild on receive event from that publisher.
Important: state variable must be used in view builder code, otherwise rendering engine would not know that something changed.
Here is simple modification of affected part of your code, that gives behaviour that you need.
#State private var refreshing = false
private var didSave = NotificationCenter.default.publisher(for: .NSManagedObjectContextDidSave)
var body: some View {
List {
ForEach(fetchedResults) { primary in
NavigationLink(destination: SecondaryView(primary: primary)) {
VStack(alignment: .leading) {
// below use of .refreshing is just as demo,
// it can be use for anything
Text("\(primary.primaryName ?? "nil")" + (self.refreshing ? "" : ""))
Text("\(primary.secondary?.secondaryName ?? "nil")").font(.footnote).foregroundColor(.secondary)
}
}
// here is the listener for published context event
.onReceive(self.didSave) { _ in
self.refreshing.toggle()
}
}
}
.navigationBarTitle("Primary List")
.navigationBarItems(trailing:
Button(action: {self.addNewPrimary()} ) {
Image(systemName: "plus")
}
)
}
An alternative method: using a Publisher and List.id():
struct ContentView: View {
/*
#FetchRequest...
*/
private var didSave = NotificationCenter.default.publisher(for: .NSManagedObjectContextDidSave) //the publisher
#State private var refreshID = UUID()
var body: some View {
List {
...
}
.id(refreshID)
.onReceive(self.didSave) { _ in //the listener
self.refreshID = UUID()
print("generated a new UUID")
}
}
}
Every time you call save() of NSManagedObjects in a context, it genertates a new UUID for the List view, and it forces the List view to refresh.
To fix that you have to add #ObservedObject to var primary: Primary in SecondaryView to work List properly. Primary belong to NSManagedObject class, which already conforms to #ObservableObject protocol. This way the changes in instances of Primary are observed.
import SwiftUI
extension Primary: Identifiable {}
// Primary View
struct PrimaryListView: View {
#Environment(\.managedObjectContext) var context
#FetchRequest(
entity: Primary.entity(),
sortDescriptors: [NSSortDescriptor(key: "primaryName", ascending: true)]
)
var fetchedResults: FetchedResults<Primary>
var body: some View {
List {
ForEach(fetchedResults) { primary in
NavigationLink(destination: SecondaryView(primary: primary)) {
VStack(alignment: .leading) {
Text("\(primary.primaryName ?? "nil")")
Text("\(primary.secondary?.secondaryName ?? "nil")").font(.footnote).foregroundColor(.secondary)
}
}
}
}
.navigationBarTitle("Primary List")
.navigationBarItems(trailing:
Button(action: {self.addNewPrimary()} ) {
Image(systemName: "plus")
}
)
}
private func addNewPrimary() {
let newPrimary = Primary(context: context)
newPrimary.primaryName = "Primary created at \(Date())"
let newSecondary = Secondary(context: context)
newSecondary.secondaryName = "Secondary built at \(Date())"
newPrimary.secondary = newSecondary
try? context.save()
}
}
struct PrimaryListView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
return NavigationView {
PrimaryListView().environment(\.managedObjectContext, context)
}
}
}
// Detail View
struct SecondaryView: View {
#Environment(\.presentationMode) var presentationMode
#ObservedObject var primary: Primary
#State private var newSecondaryName = ""
var body: some View {
VStack {
TextField("Secondary name:", text: $newSecondaryName)
.textFieldStyle(RoundedBorderTextFieldStyle())
.padding()
.onAppear {self.newSecondaryName = self.primary.secondary?.secondaryName ?? "no name"}
Button(action: {self.saveChanges()}) {
Text("Save")
}
.padding()
}
}
private func saveChanges() {
primary.secondary?.secondaryName = newSecondaryName
try? primary.managedObjectContext?.save()
presentationMode.wrappedValue.dismiss()
}
}
I tried to touch the primary object in the detail view like this:
// TODO: ❌ workaround to trigger update on primary #FetchRequest
if let primary = secondary.primary {
secondary.managedObjectContext?.refresh(primary, mergeChanges: true)
}
Then the primary list will update. But the detail view has to know about the parent object. This will work, but this is probably not the SwiftUI or Combine way...
Edit:
Based on the above workaround, I modified my project with a global save(managedObject:) function. This will touch all related Entities, thus updating all relevant #FetchRequest's.
import SwiftUI
import CoreData
extension Primary: Identifiable {}
// MARK: - Primary View
struct PrimaryListView: View {
#Environment(\.managedObjectContext) var context
#FetchRequest(
sortDescriptors: [
NSSortDescriptor(keyPath: \Primary.primaryName, ascending: true)]
)
var fetchedResults: FetchedResults<Primary>
var body: some View {
print("body PrimaryListView"); return
List {
ForEach(fetchedResults) { primary in
NavigationLink(destination: SecondaryView(secondary: primary.secondary!)) {
VStack(alignment: .leading) {
Text("\(primary.primaryName ?? "nil")")
Text("\(primary.secondary?.secondaryName ?? "nil")")
.font(.footnote).foregroundColor(.secondary)
}
}
}
}
.navigationBarTitle("Primary List")
.navigationBarItems(trailing:
Button(action: {self.addNewPrimary()} ) {
Image(systemName: "plus")
}
)
}
private func addNewPrimary() {
let newPrimary = Primary(context: context)
newPrimary.primaryName = "Primary created at \(Date())"
let newSecondary = Secondary(context: context)
newSecondary.secondaryName = "Secondary built at \(Date())"
newPrimary.secondary = newSecondary
try? context.save()
}
}
struct PrimaryListView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
return NavigationView {
PrimaryListView().environment(\.managedObjectContext, context)
}
}
}
// MARK: - Detail View
struct SecondaryView: View {
#Environment(\.presentationMode) var presentationMode
var secondary: Secondary
#State private var newSecondaryName = ""
var body: some View {
print("SecondaryView: \(secondary.secondaryName ?? "")"); return
VStack {
TextField("Secondary name:", text: $newSecondaryName)
.textFieldStyle(RoundedBorderTextFieldStyle())
.padding()
.onAppear {self.newSecondaryName = self.secondary.secondaryName ?? "no name"}
Button(action: {self.saveChanges()}) {
Text("Save")
}
.padding()
}
}
private func saveChanges() {
secondary.secondaryName = newSecondaryName
// save Secondary and touch Primary
(UIApplication.shared.delegate as! AppDelegate).save(managedObject: secondary)
presentationMode.wrappedValue.dismiss()
}
}
extension AppDelegate {
/// save and touch related objects
func save(managedObject: NSManagedObject) {
let context = persistentContainer.viewContext
// if this object has an impact on related objects, touch these related objects
if let secondary = managedObject as? Secondary,
let primary = secondary.primary {
context.refresh(primary, mergeChanges: true)
print("Primary touched: \(primary.primaryName ?? "no name")")
}
saveContext()
}
}
If you are here, i don't find the reason why your view isn't updating, i think this will help you:
Always use the #ObservedObject when you declare a core data type.
If you are using MVVM, wrap the view model also with #ObservedObject, and in the VM create the core data type with #Published.
This is an example of creating a VM with #ObservedObject, so when core data receives the update, the instance of the view model recreate itself, and the view is updated.
class ProductTitleValueViewModel: BaseViewModel, ObservableObject {
// MARK: - Properties
#Published var product: Product
var colorSet: [Color]
var currency: Currency
// MARK: - Init
init(product: Product, colorSet: [Color], currency: Currency) {
self.product = product
self.colorSet = colorSet
self.currency = currency
}
}
struct ProductTitleValueView: View {
#ObservedObject var viewModel: ProductTitleValueViewModel
var body: some View {
VStack(alignment: .leading, spacing: 5) {
HStack {
Circle()
.fill(
LinearGradient(colors: viewModel.colorSet, startPoint: .leading, endPoint: .trailing)
)
.opacity(0.6)
.frame(width: 20, height: 20)
Text(viewModel.product.wrappedName)
.font(.callout.bold())
.foregroundColor(ThemeColor.lightGray)
}
Text(viewModel.product.balance.toCurrency(with: viewModel.currency))
.font(.callout.bold())
.padding(.leading, 28)
}
}
}
If you follow this 2 simple things, you are not going to have problem with core date updating your views.
I'm trying to use TextField to change the data of an attribute of CoreData, and everything I've come up with hasn't been successful. There is a similar question (listed below), and I'm going to post the code from the correct answer to that to explain it.
struct ItemDetail: View {
#EnvironmentObject var itemStore: ItemStore
let idx: Int
var body: some View {
NavigationView {
Stepper(value: $itemStore.items[idx].inventory) {
Text("Inventory is \(self.itemStore.items[idx].inventory)")
}
// Here I would like to do this
// TextField("PlaceHolder", $itemStore.items[idx].name)
// That doesn't work... also tried
// TextField("PlaceHolder", $name) - where name is a #State String
// How can you then automaticlly assign the new value of #State name
// To $itemStore.items[idx].name?
.padding()
.navigationBarTitle(itemStore.items[idx].name)
}
}
}
Original Question:
SwiftUI #Binding doesn't refresh View
I now have it working.
struct ItemDetail: View {
#EnvironmentObject var itemStore: ItemStore
let idx: Int
// Added new #State variable
#State var name = ""
var body: some View {
NavigationView {
Stepper(value: $itemStore.items[idx].inventory) {
Text("Inventory is \(self.itemStore.items[idx].inventory)")
}
TextField("Placeholder", text: $name) {
// When the enter key is tapped, this runs.
self.itemStore.items[self.idx].name = self.name
}
.padding()
.navigationBarTitle(itemStore.items[idx].name)
}
}
}