The below swiftUI code was working fine with iOS13, but on testing with iOS14, I'm getting fatal errors caused by the force-unwrapped optional when trying to display the modal sheet. As far as I can tell, the sheet should never try to present with a nil value for selectedModel, as showingDetails is only ever made true after assigning selectedModel?
struct SpeakerBrandMenu: View {
var filteredSpeakers: [Speaker] {
// An array of Speaker objects
}
#State var selectedModel: Speaker?
#State private var showingDetails = false
var body: some View {
List{
ForEach(filteredSpeakers) { speaker in
HStack {
Button(action: {
self.selectedModel = speaker
self.showingDetails = true
}) {
SpeakerModelRow(speaker: speaker).contentShape(Rectangle())
}
.buttonStyle(PlainButtonStyle())
Spacer()
Button(
//unrelated
).padding(5)
}
}
} .sheet(isPresented: self.$showingDetails) { SpeakerDetailView(speaker: self.selectedModel!, showSheet: self.$showingDetails).environmentObject(self.favoriteSpeakers).environmentObject(self.settings)}
.navigationBarTitle(Text(brand), displayMode: .inline)
}
}
Interestingly, if I unwrap it as speaker: self.selectedModel ?? filteredSpeakers[0]it behaves exactly as expected: The first time pressing any of the menu items, the first item is passed to the sheet, but on dismissing the sheet and selecting another item it then shows the correct item every time. So it's as though the button to assign selectedModel is trying to display the sheet before it has had time assign it.
It looks like in iOS 14 the sheet(isPresented:content:) is now created beforehand, so any changes made to selectedModel are ignored.
Try using sheet(item:content:) instead:
var body: some View {
List {
...
}
.sheet(item: self.$selectedModel) {
SpeakerDetailView(speaker: $0)
}
}
and dismiss the sheet using #Environment(\.presentationMode):
struct SpeakerDetailView: View {
#Environment(\.presentationMode) private var presentationMode
var speaker: Speaker
var body: some View {
Text("Speaker view")
.onTapGesture {
presentationMode.wrappedValue.dismiss()
}
}
}
Related
Description
I've got simple Combat model which stores name and list of actors. When I delete the Combat from List using onDelete it looks like it's working. It removes the Combat from Realm (checked with RealmStudio) and updates the view. However, if view gets redrawn (for instance, when switching Apps), the "old" data is loaded again (the very first loaded on app initialization), so all deleted rows are back again. Of course, removing them again crashes the app, because they are not present in #ObservedResults combats anymore. Restarting the app fixes the issue, because new data is loaded to #ObservedResults combats and to List, but then again, when I removed something it will be back on review draw...
What I discovered is that removing .sheet() fixes the issue! (EDIT: clarification; it doesn't matter what's inside of the sheet, it may be even empty) The view is updated correctly on redraw! The Sheet is used to display form to add new Combat (nether to say that adding new combats or editing them does not update the view as well, but let's focus on deletion). I have no idea what adding sheet() changes in behaviour of the List and "listening" to #ObservedResults combats.
As a test I used simple array of Combat classes and everything worked. So it points me to issue with #ObservedResults.
I was using the Alert before and all changes to #ObservedResults combats were seen at glance. Now I wanted to replace Alert with Sheet and… That happened.
Also, I have subview where I have almost identical code for actor and there everything works, however I use #ObservedRealmObject var combat: Combat there, and I pass the combat #ObservedResults combats, like so:
NavigationLink(destination: CombatView(combat: combat)) { Text(combat.name) }
I removed unecessary code from below examples to keep it at minimum.
Model
The Combat model:
class Combat: Object, ObjectKeyIdentifiable {
#objc dynamic var id: String = UUID().uuidString
#objc dynamic var name: String = ""
var actors = List<Actor>()
}
Actual View Code (broken using Sheet)
#ObservedResults(
Combat.self,
sortDescriptor: SortDescriptor( keyPath: "name", ascending: true)
) var combats
struct CombatsListView: View {
#ObservedResults(
Combat.self,
sortDescriptor: SortDescriptor( keyPath: "name", ascending: true)
) var combats
var body: some View {
List {
ForEach(combats) { combat in
Text(combat.name)
}.onDelete(perform: $combats.remove)
}
.sheet(isPresented: $showAddCombat) {
AddCombatView( showAddCombat: $showAddCombat)
}
}
}
Old View Code (works using Alert)
struct CombatsListView: View {
#ObservedResults(
Combat.self,
sortDescriptor: SortDescriptor( keyPath: "name", ascending: true)
) var combats
#State private var showAddCombat = false
#State private var addCombatNewName = ""
var body: some View {
List(combats) { combat in
Text(combat.name)
.onDelete(perform: $combats.remove)
}
.toolbar {
ToolbarItem(placement: .navigationBarTrailing) {
Button(action: {
showAlert = true
}) {
Image(systemName: "plus" )
.font(.title)
Text("New Combat")
}.alert("New Combat", isPresented: $showAlert) {
TextField("write name", text: $addCombatNewName)
Button("Close", role: .cancel) {
addCombatNewName = ""
}
Button("Add") {
addNewCombat(name: addCombatNewName)
addCombatNewName = ""
}
}
}
}
}
private func addNewCombat(name: String) {
let newCombat = Combat()
newCombat.name = name
do {
try self.realm.write {
realm.add(newCombat)
}
} catch {
fatalError("Error: \(error)")
}
}
}
EDITED
I just found some new behaviour. I made a new simple view which lists elements of Collection list and you can delete or add new Collection. It works just fine, but if I include this CollectionsView under the TabView, then the effect is exactly the same as in the example above. The view stops working properly: deleted items are added back on view redraw and adding new objects doesn't refresh the View.
This makes me think more of a bug in #ObservedResults().
Below is the source code.
class Collection: Object, ObjectKeyIdentifiable {
#objc dynamic var id: String = UUID().uuidString
#objc dynamic var name: String = ""
var actors = List<Actor>()
}
#main
struct CombatTrackerApp: App {
var body: some Scene {
WindowGroup {
Tabber() // will not work
// CollectionsView() // will work
}
}
}
struct CollectionsView: View {
#ObservedResults( Collection.self ) var collections
#State private var showNewCollectionForm = false
var body: some View {
NavigationStack {
List {
ForEach(collections) { collection in
Text(collection.name)
}.onDelete(perform: $collections.remove)
}
.listStyle(.inset)
.padding()
.navigationTitle("Collections")
.toolbar {
ToolbarItem(placement: .navigationBarTrailing) {
Button() {
self.showNewCollectionForm.toggle()
} label: {
Image(systemName: "plus")
Text("Add New Collection")
}
}
}
.sheet(isPresented: $showNewCollectionForm) {
NewCollectionView( showNewCollectionForm: $showNewCollectionForm )
}
}
}
}
struct NewCollectionView: View {
let realm = try! Realm()
#Binding var showNewCollectionForm: Bool
#State private var newCollectioName: String = ""
var body: some View {
NavigationStack {
VStack {
Text("Create new Collection").font(.title).padding()
Form {
TextField("Name", text: $newCollectioName)
}
}
.navigationBarTitleDisplayMode(.inline)
.toolbar {
ToolbarItem(placement: .navigationBarLeading) {
Button("Close", role: .cancel) {
showNewCollectionForm.toggle()
}
}
ToolbarItem {
Button("Create") {
addCollection()
} .disabled(newCollectioName.isEmpty)
}
}
}
}
private func addCollection() {
let newCollection = Collection()
newCollection.name = newCollectioName
do {
try realm.write {
realm.add(newCollection)
}
} catch {
print("Cannot add new Collection", error)
}
showNewCollectionForm.toggle()
}
}
struct Tabber: View {
var body: some View {
TabView() {
NavigationStack {
CombatsListView()
}
.tabItem {
Text("Combats")
}
NavigationStack {
CollectionsView()
}
.tabItem {
Text("Collections")
}
SettingsView()
.tabItem {
Text("Settings")
}
}
}
}
I found out the solution (but I still don't understand why it's working).
The solution was to move NavigationStack from my TabView to the subviews. So instead of:
struct Tabber: View {
var body: some View {
TabView() {
NavigationStack {
CombatsListView()
}
.tabItem {
Text("Combats")
}
//...
I should do:
struct Tabber: View {
var body: some View {
TabView() {
CombatsListView()
.tabItem {
Text("Combats")
}
//...
struct CombatsListView: View {
var body: some View {
NavigationStack {
Confusing part was that all online tutorials and Apple Documentation suggests to wrap subviews with NavigationStack in TabView directly instead of adding NavigationStack in subviews. Maybe it's a bug, maybe it's a feature.
Here is a simple list view of "Topic" struct items. The goal is to present an editor view when a row of the list is tapped. In this code, tapping a row is expected to cause the selected topic to be stored as "tappedTopic" in an #State var and sets a Boolean #State var that causes the EditorV to be presented.
When the code as shown is run and a line is tapped, its topic name prints properly in the Print statement in the Button action, but then the app crashes because self.tappedTopic! finds tappedTopic to be nil in the EditTopicV(...) line.
If the line "tlVM.objectWillChange.send()" is uncommented, the code runs fine. Why is this needed?
And a second puzzle: in the case where the code runs fine, with the objectWillChange.send() uncommented, a print statement in the EditTopicV init() shows that it runs twice. Why?
Any help would be greatly appreciated. I am using Xcode 13.2.1 and my deployment target is set to iOS 15.1.
Topic.swift:
struct Topic: Identifiable {
var name: String = "Default"
var iconName: String = "circle"
var id: String { name }
}
TopicListV.swift:
struct TopicListV: View {
#ObservedObject var tlVM: TopicListVM
#State var tappedTopic: Topic? = nil
#State var doEditTappedTopic = false
var body: some View {
VStack(alignment: .leading) {
List {
ForEach(tlVM.topics) { topic in
Button(action: {
tappedTopic = topic
// why is the following line needed?
tlVM.objectWillChange.send()
doEditTappedTopic = true
print("Tapped topic = \(tappedTopic!.name)")
}) {
Label(topic.name, systemImage: topic.iconName)
.padding(10)
}
}
}
Spacer()
}
.sheet(isPresented: $doEditTappedTopic) {
EditTopicV(tlVM: tlVM, originalTopic: self.tappedTopic!)
}
}
}
EditTopicV.swift (Editor View):
struct EditTopicV: View {
#ObservedObject var tlVM: TopicListVM
#Environment(\.presentationMode) var presentationMode
let originalTopic: Topic
#State private var editTopic: Topic
#State private var ic = "circle"
let iconList = ["circle", "leaf", "photo"]
init(tlVM: TopicListVM, originalTopic: Topic) {
print("DBG: EditTopicV: originalTopic = \(originalTopic)")
self.tlVM = tlVM
self.originalTopic = originalTopic
self._editTopic = .init(initialValue: originalTopic)
}
var body: some View {
VStack(alignment: .leading) {
HStack {
Button("Cancel") {
presentationMode.wrappedValue.dismiss()
}
Spacer()
Button("Save") {
editTopic.iconName = editTopic.iconName.lowercased()
tlVM.change(topic: originalTopic, to: editTopic)
presentationMode.wrappedValue.dismiss()
}
}
HStack {
Text("Name:")
TextField("name", text: $editTopic.name)
Spacer()
}
Picker("Color Theme", selection: $editTopic.iconName) {
ForEach(iconList, id: \.self) { icon in
Text(icon).tag(icon)
}
}
.pickerStyle(.segmented)
Spacer()
}
.padding()
}
}
TopicListVM.swift (Observable Object View Model):
class TopicListVM: ObservableObject {
#Published var topics = [Topic]()
func append(topic: Topic) {
topics.append(topic)
}
func change(topic: Topic, to newTopic: Topic) {
if let index = topics.firstIndex(where: { $0.name == topic.name }) {
topics[index] = newTopic
}
}
static func ex1() -> TopicListVM {
let tvm = TopicListVM()
tvm.append(topic: Topic(name: "leaves", iconName: "leaf"))
tvm.append(topic: Topic(name: "photos", iconName: "photo"))
tvm.append(topic: Topic(name: "shapes", iconName: "circle"))
return tvm
}
}
Here's what the list looks like:
Using sheet(isPresented:) has the tendency to cause issues like this because SwiftUI calculates the destination view in a sequence that doesn't always seem to make sense. In your case, using objectWillSend on the view model, even though it shouldn't have any effect, seems to delay the calculation of your force-unwrapped variable and avoids the crash.
To solve this, use the sheet(item:) form:
.sheet(item: $tappedTopic) { item in
EditTopicV(tlVM: tlVM, originalTopic: item)
}
Then, your item gets passed in the closure safely and there's no reason for a force unwrap.
You can also capture tappedTopic for a similar result, but you still have to force unwrap it, which is generally something we want to avoid:
.sheet(isPresented: $doEditTappedTopic) { [tappedTopic] in
EditTopicV(tlVM: tlVM, originalTopic: tappedTopic!)
}
I am using coredata to save information. This information populates a picker, but at the moment there is no information so the picker is empty. The array is set using FetchedRequest.
#FetchRequest(sortDescriptors: [])
var sources: FetchedResults<Source>
#State private var selectedSource = 0
This is how the picker is setup.
Picker(selection: $selectedSource, label: Text("Source")) {
ForEach(0 ..< sources.count) {
Text(sources[$0].name!)
}
}
There is also a button that displays another sheet and allows the user to add a source.
Button(action: { addSource.toggle() }, label: {
Text("Add Source")
})
.sheet(isPresented: $addSource, content: {
AddSource(showSheet: $addSource)
})
If the user presses Add Source, the sheet is displayed with a textfield and a button to add the source. There is also a button to dismiss the sheet.
struct AddSource: View {
#Environment(\.managedObjectContext) var viewContext
#Binding var showSheet: Bool
#State var name = ""
var body: some View {
NavigationView {
Form {
Section(header: Text("Source")) {
TextField("Source Name", text: $name)
Button("Add Source") {
let source = Source(context: viewContext)
source.name = name
do {
try viewContext.save()
name = ""
} catch {
let error = error as NSError
fatalError("Unable to save context: \(error)")
}
}
}
}
.navigationBarTitle("Add Source")
.navigationBarItems(trailing: Button(action:{
self.showSheet = false
}) {
Text("Done").bold()
.accessibilityLabel("Add your source.")
})
}
}
}
Once the sheet is dismissed, it goes back to the first view. The picker in the first view is not updated with the newly added source. You have to close it and reopen. How can I update the picker once the source is added by the user? Thanks!
The issue is with the ForEach signature you're using. It works only for constant data. If you want to use with changing data, you have to use something like:
ForEach(sources, id: \Source.name.hashValue) {
Text(verbatim: $0.name!)
}
Note that hashValue will not be unique for two entity objects with the same name. This is just an example
I have a sheet view that is presented when a user clicks a button as shown in the parent view below:
struct ViewWithSheet: View {
#State var showingSheetView: Bool = false
#EnvironmetObject var store: DataStore()
var body: some View {
NavigationView() {
ZStack {
Button(action: { self.showingSheetView = true }) {
Text("Show sheet view")
}
}
.navigationBarHidden(true)
.navigationBarTitle("")
.sheet(isPresented: $showingSheetView) {
SheetView(showingSheetView: self.$showingSheetView).environmentObject(self.dataStore)
}
}
}
}
In the sheet view, when a user clicks another button, an action is performed by the store that has a completion handler. The completion handler returns an object value, and if that value exists, should dismiss the SheetView.
struct SheetView: View {
#Binding var showingSheetView: Bool
#EnvironmentObject var store: DataStore()
//#Environment(\.presentationMode) private var presentationMode
func create() {
store.createObject() { object, error in
if let _ = object {
self.showingSheetView = false
// self.presentationMode.wrappedValue.dismiss()
}
}
}
var body: some View {
VStack {
VStack {
HStack {
Button(action: { self.showingSheetView = false }) {
Text("Cancel")
}
Spacer()
Spacer()
Button(action: { self.create() }) {
Text("Add")
}
}
.padding()
}
}
}
}
However, in the create() function, once the store returns values and showingSheetView is set to false, the sheet view doesn't dismiss as expected. I've tried using presentationMode to dismiss the sheet as well, but this also doesn't appear to work.
I found my issue, the sheet wasn't dismissing due to a conditional in my overall App wrapping View, I had an if statement that would show a loading view on app startup, however, in my DataStore I was setting it's fetching variable on every function call it performs. When that value changed, the view stack behind my sheet view would re-render the LoadingView and then my TabView once the fetching variable changed again. This was making the sheet view un-dismissable. Here's an example of what my AppView looked like:
struct AppView: View {
#State private var fetchMessage: String = ""
#EnvironmentObject var store: DataStore()
func initializeApp() {
self.fetchMessage = "Getting App Data"
store.getData() { object, error in
if let error = error {
self.fetchMessage = error.localizedDescription
}
self.fetchMessage = ""
}
}
var body: some View {
Group {
ZStack {
//this is where my issue was occurring
if(!store.fetching) {
TabView {
Tab1().tabItem {
Image(systemName: "tab-1")
Text("Tab1")
}
Tab2().tabItem {
Image(systemName: "tab-2")
Text("Tab2")
}
//Tab 3 contained my ViewWithSheet() and SheetView()
Tab3().tabItem {
Image(systemName: "tab-3")
Text("Tab3")
}
}
} else {
LoadingView(loadingMessage: $fetchMessage)
}
}
}.onAppear(perform: initializeApp)
}
}
To solve my issue, I added another variable to my DataStore called initializing, which I use to render the loading screen or the actual application views on first .onAppear event in my app. Below is an example of what my updated AppView looks like:
struct AppView: View {
#State private var fetchMessage: String = ""
#EnvironmentObject var store: DataStore()
func initializeApp() {
self.fetchMessage = "Getting App Data"
store.getData() { object, error in
if let error = error {
self.fetchMessage = error.localizedDescription
}
self.fetchMessage = ""
//set the value to false once I'm done getting my app's initial data.
self.store.initializing = false
}
}
var body: some View {
Group {
ZStack {
//now using initializing instead
if(!store.initializing) {
TabView {
Tab1().tabItem {
Image(systemName: "tab-1")
Text("Tab1")
}
Tab2().tabItem {
Image(systemName: "tab-2")
Text("Tab2")
}
//Tab 3 contained my ViewWithSheet() and SheetView()
Tab3().tabItem {
Image(systemName: "tab-3")
Text("Tab3")
}
}
} else {
LoadingView(loadingMessage: $fetchMessage)
}
}
}.onAppear(perform: initializeApp)
}
}
Try to do this on main queue explicitly
func create() {
store.createObject() { object, error in
if let _ = object {
DispatchQueue.main.async {
self.showingSheetView = false
}
}
// think also about feedback on else case as well !!
}
}
Want to see something hacky that worked for me? Disclaimer: Might not work for you and I don't necessarily recommend it. But maybe it'll help someone in a pinch.
If you add a NavigationLink AND keep your fullScreenCover, then the fullscreen cover will be able to dismiss itself like you expect.
Why does this happen when you add the NavigationLink to your View? I don't know. My guess is it creates an extra reference somewhere.
Add this to your body, and keep your sheet as it is:
NavigationLink(destination: YOURVIEW().environmentObjects(), isActive: $showingSheetView) {}
I have a very simple schoolbook example of a SwiftUI List view that renders items from data in an array. Data in the array is Identifiable. But, when I change the the data in the array, add or remove a item then all rows in the list view are recreated. Is that correct? My understanding was that Identifiable should make sure that only the view in the list that are changed are recreated.
My list is inside a navigation view and each row links to a detail view. The problem is that since all items in the list are removed and recreated every time the data is changed then if that that happens when Im in a detail view (it's triggered by a notification) then Im thrown out back to the list.
What am I missing?
Edit: Added code example
This is my data struct:
struct Item: Identifiable {
let id: UUID
let name: String
init(name: String) {
self.id = UUID()
self.name = name
}
}
This is my ItemView
struct ItemView: View {
var item: Item
init(item: Item) {
self.item = item
print("ItemView created \(self.item.id)")
}
var body: some View {
Text(self.item.name)
}
}
An finally my list view:
struct KeyList: View {
#State var items = [Item(name: "123"), Item(name: "456"), Item(name: "789")]
var body: some View {
VStack {
List(self.items) { item in
ItemView(item: item)
}
Button(action: {
self.items.append(Item(name: "New"))
}) {
Text("Add")
}
}
}
}
When I press add it will print "ItemView created" 4 times. My understanding is that it should only do it 1 time?
Here is an example of how this could work. Tested and working on iOS 13.5
The List doesn't get recreated again when only one item is being removed. So this was accomplished.
About the poping of the View this has already been answered here:
SwiftUI ForEach refresh makes view pop
I have here a small workaround for this problem. Add the items you want to remove to an array. Then when going back, remove these items (Which will make the view pop) or go back programmatically and nothing gets removed
struct ContentView: View {
#State var text:Array<String> = ["a", "b", "c"]
var body: some View {
NavigationView() {
VStack() {
List() {
ForEach(self.text, id: \.self){ item in
NavigationLink(destination: SecondView(textItem: item, text: self.$text)) {
Text(item)
}
}
}
Button(action: {
self.text.remove(at: 0)
}){
Text("Remove \(self.text[0])")
}
}
}
}
}
struct SecondView: View {
#State var textItem: String
#Binding var text: Array<String>
#State var tmpArray: Array<String> = []
#Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
var body: some View {
VStack() {
Text(self.textItem)
Button(action: {
//Append to a tmp array which will later be used to determine what to remove
self.tmpArray.append(self.text[0])
}){
Text("Remove \(self.text[0])")
}
Button(action: {
if self.tmpArray.count > 0 {
//remove your stuff which will automatically pop the view
self.text.remove(at: 0)
} else {
// programmatically go back as nothing has been deleted
self.presentationMode.wrappedValue.dismiss()
}
}){
Text("Go Back")
}
}
}
}