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)
}
}
}
Related
clueless beginner here. Apologies if my question is formed poorly. This is the first time I ask a question of this scale and I have a hard time balancing between posting too much code for the good samaritans to read and too little to post an effective question. Huge thanks in advance!
I am trying to incorporate the textfieldalert in this post in my learner project. There are two Swift files in questions: File A (PosTextFieldAlertView) has an extension that needs to use two functions in File B (ListView).
These are the functions I need to use in File A.
func addPositive(){
let newPositive = PositiveEntity(context: viewContext)
newPositive.title = alertInput
save()
}
func save() {
do { try viewContext.save() } catch { print(error) }
}
I thought of/researched two methods: 1) duplicate the function in File A or 2) create instance of the view in File B that contains that functions according this post. However I ran into problems in both methods.
Duplicating the functions:
I copied the CoreData related properties in the PosTextFieldAlert struct. But now PosTextFieldAlert in the return part of the extension has the error of "Missing arguments for parameters [Core Data properties] in call". I don’t know how to set the property in the extension without referring or creating a different sets of Core Data entities.
Creating an instance of the relevant view
In the instance creation I would need to input the arguments but I don’t know how to refer to the same NSManagedObjectContext.
Code excerpts:
PosTextFieldAlertView
struct PosTextFieldAlert<Presenting>: View where Presenting: View {
var viewContext: NSManagedObjectContext
var positives: [PositiveEntity]
var targets: [TargetEntity]
#State private var alertInput = ""
// let listView = ListView(viewContext: NSManagedObjectContext, positives: PositiveEntity, negatives: NegativeEntity, targets: TargetEntity)
#Binding var isShowing: Bool
#Binding var text: String
let presenting: Presenting
let title: String
var body: some View {
GeometryReader { (deviceSize: GeometryProxy) in
ZStack {
self.presenting
.disabled(isShowing)
VStack {
Text(self.title)
TextField(self.title, text: self.$text)
Divider()
VStack{
HStack {
Button(action: {
withAnimation {
self.isShowing.toggle()
}
}) {
Text("+")
}.padding()
Button(action: {
withAnimation {
self.isShowing.toggle()
}
}) {
Text("-")
}.padding()
}
Button(action: {
withAnimation {
self.isShowing.toggle()
}
}) {
Text("Done")
}
}
}
.padding()
.background(Color.white)
.frame(
width: deviceSize.size.width*0.7,
height: deviceSize.size.height*0.7
)
.shadow(radius: 1)
.opacity(self.isShowing ? 1 : 0)
}
}
}
func addPositive(){
let newPositive = PositiveEntity(context: viewContext)
newPositive.title = alertInput
save()
}
func save() {
do { try viewContext.save() } catch { print(error) }
}
}
extension View {
func posTextFieldAlert(isShowing: Binding<Bool>,
text: Binding<String>,
title: String) -> some View {
PosTextFieldAlert(isShowing: isShowing,
text: text,
presenting: self,
title: title)
}
}
The code in ListView
struct ListView: View {
var viewContext: NSManagedObjectContext
var positives: [PositiveEntity]
var negatives: [NegativeEntity]
var targets: [TargetEntity]
//[layout of the project]
}
The Fetchrequests in ContentView:
#Environment(\.managedObjectContext) var viewContext
#FetchRequest(sortDescriptors: []) var targets: FetchedResults<TargetEntity>
#FetchRequest(sortDescriptors: []) var positives: FetchedResults<PositiveEntity>
#FetchRequest(sortDescriptors: []) var negatives: FetchedResults<NegativeEntity>
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 have a parent view which does a #FetchRequest and passes the FetchedResults<T> to a child view. Everything works, and the child view is able to parse through the FetchedResults. However, I can't figure out how to set up the data so that the child's Preview struct will work. What's the proper way to set up some constant data in Preview struct so that I can instantiate the child view and pass in FetchedResults<T>?
As FetchedResults<T> is a RandomAccessCollection and swift array also is a RandomAccessCollection, here is possible solution.
Update: verified with Xcode 13.3 / iOS 15.4
struct ContentView: View {
#Environment(\.managedObjectContext) var context
#FetchRequest(entity: Person.entity(), sortDescriptors: [])
var result: FetchedResults<Person>
var body: some View {
VStack(alignment: .leading) {
Text("Persons").font(.title)
PersonsView(results: result) // FetchedResults<Person> is a collection
}
}
}
// generalize PersonsView to depend just on collection
struct PersonsView<Results:RandomAccessCollection>: View where Results.Element == Person {
let results: Results
var body: some View {
ForEach(results, id: \.self) { person in
Text("Name: \(person.name ?? "<unknown>")")
}
}
}
// Tested with Xcode 11.4 / iOS 13.4
// DOES NOT WORK ANYMORE !!
// struct ChildView_Previews: PreviewProvider {
// static var previews: some View {
// PersonsView(results: [Person()]) // << use regular array //to test
// }
}
Update: fixed & tested part for Xcode 12 / iSO 14 (due to crash of above PreviewProvider)
It appears entity now should be read & specified explicitly:
struct ChildView_Previews: PreviewProvider {
static let entity = NSManagedObjectModel.mergedModel(from: nil)?.entitiesByName["Person"]
static var previews: some View {
let person = Person(entity: entity!, insertInto: nil)
person.name = "Test Name"
return PersonsView(results: [person])
}
}
Use the preview PersistenceController within your pre-generated PersistenceController struct (inside the "Persistence.swift" file).
so if you pass an item from a Core Data "Item"-entity:
struct ContentView: View {
...
private var items: FetchedResults<Item>
..
ForEach(items) { item in
DetailView(item: item)
}
..
In the Detail-View go like this:
struct DetailView: View {
var item: FetchedResults<Item>.Element
var body: some View {
Text("Items text = \(item.text ?? "")")
}
}
struct Detail_Previews: PreviewProvider {
static var previews: some View {
let viewContext = PersistenceController.preview.container.viewContext
let previewItem = Item(context: viewContext)
previewItem.text = "Text4preview"
return Detail(item: previewItem)
}
}
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 have a file called PDFManager , which is in charge to create and save the pdf file.
on PDFManager I create the var nameCPT : String = "" and from the ContentView i'm try to fill this var with a value from a textfield
problem is, Xcode give me the error say "Cannot convert value of type 'String' to expected argument type 'Binding'"
I tried on pdf manager create a var with #State but still not working
any idea how to pass the value of my textField to PDFManager?
thanks
import SwiftUI
struct ContentView: View {
var lm : PDFManager
var body: some View {
VStack {
fakebar
Spacer()
HStack {
TextField("Insert Nome CPT", text: lm.nameCPT).
// not working, I try with $lm.nameCPT but still not working
.padding(.leading)
}
Spacer()
}
}
You need to use #Observed property wrapper to allow the property being observed and comply with ObservableObject in your PDFManager class.
class PDFManager:ObservableObject {
var nameCPT:String = "test"
}
struct ContentView: View {
#ObservedObject var lm : PDFManager = PDFManager()
var body: some View {
VStack {
Spacer()
HStack {
TextField("Insert Nome CPT", text: $lm.nameCPT)
.padding(.leading)
Button(action:{
// Prints the value stored in your PDF manager
print(self.lm.nameCPT)
}){
Text("Check")
}
}
Spacer()
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}