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
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>
self-learning beginner here. I am trying to show an Int from Core Data in a VStack in ContentView, not in a List. But literally all the tutorials I can find about Core Data (tracking Books, Movies, Orders, Students) are using a List to show an array containing an Int. Nothing on showing an Int by itself.
Xcode can build countnum.countnum +=1 with no problem. Seems to me it is reading it fine. But once I try to show it, it just doesn’t work. I’m wrecking my brain here.
struct ContentView: View {
#Environment(\.managedObjectContext) var moc
#FetchRequest(sortDescriptors: []) var countnum: FetchedResults<CountNum>
var body: some View {
// let countnum = CountNum(context: moc)
VStack{
Text("+")
.padding()
.onTapGesture (count: 2){
let countnum = CountNum(context: moc)
countnum.countnum += 1
}
Text("\(countnum)") //No exact matches in call to instance method 'appendInterpolation'
}
}
}
Thanks
....all the tutorials ... show an array containing an Int. Yes, that's because CoreData
can contain many "objects". You get an array of your CountNum objects when
you do your .....var countnum: FetchedResults<CountNum>. So you need to decide which CountNum you want to
use. For example, if you want to use the first one, then:
struct ContentView: View {
#Environment(\.managedObjectContext) var moc
#FetchRequest(sortDescriptors: []) var countnum: FetchedResults<CountNum>
var body: some View {
VStack {
if let firstItem = countnum.first {
Text("+")
.padding()
.onTapGesture(count: 2) {
firstItem.countnum += 1
do {
try moc.save()
} catch {
print(error)
}
}
Text("\(firstItem.countnum)").foregroundColor(.green)
}
}
}
}
EDIT-1: adding new CountNum to CoreData example code in the add button.
struct ContentView: View {
#Environment(\.managedObjectContext) var moc
#FetchRequest(sortDescriptors: []) var countnum: FetchedResults<CountNum>
var body: some View {
Button(action: {add()}) { Text("add new CountNum").foregroundColor(.green) }
.padding(.top, 50)
List {
ForEach(countnum) { item in
HStack {
Text("++")
.onTapGesture(count: 2) { increment(item) }
Text("\(item.countnum)").foregroundColor(.blue)
Text("delete").foregroundColor(.red)
.onTapGesture { delete(item: item) }
}
}
}
}
func increment(_ item: CountNum) {
item.countnum += 1
save()
}
func add() {
let countnum = CountNum(context: moc)
countnum.countnum = 0
save()
}
func delete(item: CountNum) {
moc.delete(item)
save()
}
func save() {
do { try moc.save() } catch { print(error) }
}
}
I am using a TabView/NavigationView & NavigationLink to programmatically navigate from a list view to detailed view and when I update the boolean property 'pinned' to true & save the core data entity in the detailed view, I am getting the following unfortunate side effects:
an involuntary navigation back to the list view and then again back to the detailed view or
an involuntary navigation to another copy of the same detailed view and then back to the list view.
I have prepared a small Xcode project with the complete sample code
In the list view I use #FetchRequest to query the list and sort on the following:
#FetchRequest(entity: Task.entity(),sortDescriptors: [NSSortDescriptor(key: "pinned", ascending: false),
NSSortDescriptor(key: "created", ascending: true),
NSSortDescriptor(key: "name", ascending: true)])
In the list view I use the following:
List() {
ForEach(tasks, id: \.self) { task in
NavigationLink(destination: DetailsView(task: task), tag: task.id!.uuidString, selection: self.$selectionId) {
HStack() {
...
}
}
}
.
(1) If I omit the 'NSSortDescriptor(key: "pinned" ...)' I don't see the behavior.
(2) If I omit the 'tag:' and the 'selection:' parameters in the NavigationLink() I don't see the behavior. But I need to be able to trigger the navigation link programmatically when I create a new Task entity.
(3) It seems never to happen when I have a single entity in the list or changing the value of the 'pinned' boolean property in the first entity in the list.
(4) I get the warning:
[TableView] Warning once only: UITableView was told to layout its visible cells and other contents without being in the view hierarchy (the table view or one of its superviews has not been added to a window)...
The parent view to the list view (TasksListView) contains a TabView:
struct ContentView: View {
var body: some View {
TabView {
NavigationView {
TasksListView()
}
.tabItem {
Image(systemName: "tray.full")
.font(.title)
Text("Master")
}
NavigationView {
EmptyView()
}
.tabItem {
Image(systemName: "magnifyingglass")
.font(.title)
Text("Search")
}
}
}
}
struct TasksListView: View {
// NSManagedObjectContext
#Environment(\.managedObjectContext) var viewContext
// Results of fetch request for tasks:
#FetchRequest(entity: Task.entity(),sortDescriptors: [NSSortDescriptor(key: "pinned", ascending: false),
NSSortDescriptor(key: "created", ascending: true),
NSSortDescriptor(key: "name", ascending: true)])
var tasks: FetchedResults<Task>
// when we create a new task and navigate to it programitically
#State var selectionId : String?
#State var newTask : Task?
var body: some View {
List() {
ForEach(tasks, id: \.self) { task in
NavigationLink(destination: DetailsView(task: task), tag: task.id!.uuidString, selection: self.$selectionId) {
HStack() {
VStack(alignment: .leading) {
Text("\(task.name ?? "unknown")")
.font(Font.headline.weight(.light))
.padding(.bottom,5)
Text("Created:\t\(task.created ?? Date(), formatter: Self.dateFormatter)")
.font(Font.subheadline.weight(.light))
.padding(.bottom,5)
if task.due != nil {
Text("Due:\t\t\(task.due!, formatter: Self.dateFormatter)")
.font(Font.subheadline.weight(.light))
.padding(.bottom,5)
}
}
}
}
}
}
.navigationBarTitle(Text("Tasks"),displayMode: .inline)
.navigationBarItems(trailing: rightButton)
}
var rightButton: some View {
Image(systemName: "plus.circle")
.foregroundColor(Color(UIColor.systemBlue))
.font(.title)
.contentShape(Rectangle())
.onTapGesture {
// create a new task and navigate to it's detailed view to add values
Task.create(in: self.viewContext) { (task, success, error) in
if success {
self.newTask = task
self.selectionId = task!.id!.uuidString
}
}
}
}
}
struct DetailsView: View {
// NSManagedObjectContext
#Environment(\.managedObjectContext) var viewContext
#ObservedObject var task : Task
#State var name : String = ""
#State var dueDate : Date = Date()
#State var hasDueDate : Bool = false
#State var isPinned : Bool = false
var body: some View {
List() {
Section() {
Toggle(isOn: self.$isPinned) {
Text("Pinned")
}
}
Section() {
TextField("Name", text: self.$name)
.font(Font.headline.weight(.light))
Text("\(task.id?.uuidString ?? "unknown")")
.font(Font.headline.weight(.light))
}
Section() {
HStack() {
Text("Created")
Spacer()
Text("\(task.created ?? Date(), formatter: Self.dateFormatter)")
.font(Font.subheadline.weight(.light))
}
Toggle(isOn: self.$hasDueDate) {
Text("Set Due Date")
}
if self.hasDueDate {
DatePicker("Due Date", selection: self.$dueDate, in: Date()... , displayedComponents: [.hourAndMinute, .date])
}
}
}
.navigationBarTitle(Text("Task Details"),displayMode: .inline)
.navigationBarItems(trailing: rightButton)
.listStyle(GroupedListStyle())
.onAppear() {
if self.task.pinned {
self.isPinned = true
}
if self.task.name != nil {
self.name = self.task.name!
}
if self.task.due != nil {
self.dueDate = self.task.due!
self.hasDueDate = true
}
}
}
// save button
var rightButton: some View {
Button("Save") {
// save values in task & save:
self.task.pinned = self.isPinned
if self.hasDueDate {
self.task.due = self.dueDate
}
if self.name.count > 0 {
self.task.name = self.name
}
Task.save(in: self.viewContext) { (success, error) in
DispatchQueue.main.async {
if success {
print("Task saved")
}
else {
print("****** Error: Task can't be saved, error = \(error!.localizedDescription)")
}
}
}
}
.contentShape(Rectangle())
}
}
extension Task {
static func save(in managedObjectContext: NSManagedObjectContext, completion: #escaping (Bool, NSError?) -> Void ) {
managedObjectContext.performAndWait() {
do {
try managedObjectContext.save()
completion(true, nil)
} catch {
let nserror = error as NSError
print("****** Error: Unresolved error \(nserror), \(nserror.userInfo)")
completion(false, nserror)
}
}
}
}
Any suggestions?
You seem to be creating your tab view in a different way than me. Those extra navigation views made cause an issue.
Not sure if it will help or not but I do it like that:
struct ContentView: View {
var body: some View {
TabView {
TasksListView()
.tabItem {
Image(systemName: "tray.full")
.font(.title)
Text("Master")
}
EmptyView()
.tabItem {
Image(systemName: "magnifyingglass")
.font(.title)
Text("Search")
}
}
}
}
This is a bug in iOS 13.
It has been fixed since iOS 14.0 beta 3.
You will find a similar question here (the accepted answer provides a workaround):
Issue when rearranging List item in detail view using SwiftUI Navigation View and Sorted FetchRequest
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()
}
}