I have this Store struct, which is a wrapper for all my data. It has a subscript operator which takes in a UUID, and returns the associated object.
This way, I can have a List bind to a selection variable, which has type UUID, and then in another view I can access the selected object from that UUID.
However, I'm experiencing an issue where my TextField which binds to the Store doesn't update. It does update if I wrap it in another Binding, or if I instead just use Text.
Here is an minimal reproducible example:
struct Person: Identifiable, Hashable {
let id = UUID()
var name: String
}
struct Store {
var data: [Person]
subscript(id: Person.ID) -> Person {
get {
data.first(where: { $0.id == id })!
}
set {
data[data.firstIndex(where: { $0.id == id })!] = newValue
}
}
}
struct ContentView: View {
#State var store = Store(data: [
Person(name: "Joe"),
Person(name: "Eva"),
Person(name: "Sam"),
Person(name: "Mary")
])
#State var selection: Person.ID?
var body: some View {
NavigationView {
List(store.data, selection: $selection) {
Text($0.name)
}
if let selection = selection {
// Creating a new Binding which simply wraps $store[selection].name
// fixes this issue. Or just using Text also works.
TextField("Placeholder", text: $store[selection].name)
}
else {
Text("No Selection")
}
}
}
}
To reproduce this issue, just click different names on the Sidebar. For some reason the detail view's TextField doesn't update!
This issue can also be resolved if we simply move the Store to a ObservableObject class with #Published.
Also, making the Store conform to Hashable doesn't help this issue.
I feel like I'm missing something very basic with SwiftUI. Is there any way to fix this?
EDIT:
I've changed out Store for an [Person], and I made an extension with the same subscript operator that is in Store. However, the problem still remains!
try this:
TextField("Placeholder", text: $store[selection].name)
.id(selection) // <-- here
Related
EDITS:
removed id: \.self
removed .onDelete from List (mistake in editing)
removed removeRows function
change the Note struct to only hash the id
I am making an app in swiftUI that returns a list of notes. I have a struct, note, that is defined as follows:
struct Note: Identifiable, Hashable {
let id = UUID()
var title: String
var content: String
func hash(into hasher: inout Hasher) {
hasher.combine(id)
}
}
It conforms to Identifiable so that it can be selected inside a List, and it conforms to Hashable so that it can be held inside a Set (for selection).
My view that (I think) is being super slow and eventually crashing is as follows:
struct SearchView: View {
#State private var searchValue: String = ""
#State private var searchResults: [Note] = [
Note(title: "Hi", content: "whats up"),
Note(title: "wassup", content: "hi")
]
#State private var selectKeeper = Set<Note>()
var body: some View {
VStack(alignment: .leading) {
SearchInputView(searchValue: $searchValue, searchResults: $searchResults)
List(searchResults, selection: $selectKeeper) { note in
Text(note.title )
}
}
}
}
SearchInputView is basically just a view that uses combine to run this function on the contents of a textfield every keypress:
func findIn(notes: [Note], pattern: String) -> [Note] {
if pattern.isEmpty { return notes }
var matchedNotes: [Note] = []
for note in notes {
let note = Note(title: note.title.uppercased(), content: note.content.uppercased())
let pattern = pattern.uppercased()
if note.title.contains(pattern) || note.content.contains(pattern) {
matchedNotes.append(note)
}
}
return matchedNotes
}
This all used to work fine with a ForEach loop and the Note struct not conforming to Identifiable, but right now for whatever reason, the app crashes as soon as I type anything into the text box. I have no idea why this is happening, and I can't see anything in the profilers that might tell me what's going on. The only thing is that as soon as I type all of the uses goes up to 100% and the app crashes. Any ideas?
Thanks!
I figured out that my problem was due to putting the findIn function outside of the struct that was using it. I am not at all sure why this is, but putting it inside of the struct calling it caused it to work out fine. Thanks so much to everyone who provided helpful suggestions in the comments!
Sorry to make this post so long, but in hindsight I should have shown you the simpler instance of the issue so you could better understand what the problem is. I am assuming the same issue with ForEach is at the root cause of both of these bugs, but I could be wrong. The second instance is still included to give you context, but the first intance should be all you need to fully understand the issue.
First Instance:
Here is a video of the issue: https://imgur.com/a/EIg9TSm. As you can see, there are 4 Time Codes, 2 of which are favorite and 2 are not favorites (shown by the yellow star). Additionally, there is text at the top that represents the array of Time Codes being displayed just as a list of favorite (F) or not favorite (N). I click on the last Time Code (Changing to favorite) and press the toggle to unfavorite it. When I hit save, the array of Time Codes is updated, yet as you see, this is not represented in the List. However, you see that the Text of the reduced array immediately updates to FNFF, showing that it is properly updated as a favorite by the ObservedObject.
When I click back on the navigation and back to the page, the UI is properly updated and there are 3 yellow stars. This makes me assume that the problem is with ForEach, as the Text() shows the array is updated but the ForEach does not. Presumably, clicking out of the page reloads the ForEach, which is why it updates after exiting the page. EditCodeView() handles the saving of the TimeCodeVieModel in CoreData, and I am 99% certain that it works properly through my own testing and the fact that the ObservedObject updates as expected. I am pretty sure I am using the dynamic version of ForEach (since TimeCodeViewModel is Identifiable), so I don't know how to make the behavior update immediately after saving. Any help would be appreciated.
Here is the code for the view:
struct ListTimeCodeView: View {
#ObservedObject var timeCodeListVM: TimeCodeListViewModel
#State var presentEditTimeCode: Bool = false
#State var timeCodeEdit: TimeCodeViewModel?
init() {
self.timeCodeListVM = TimeCodeListViewModel()
}
var body: some View {
VStack {
HStack {
Text("TimeCodes Reduced by Favorite:")
Text("\(self.timeCodeListVM.timeCodes.reduce(into: "") {$0 += $1.isFavorite ? "F" : "N"})")
}
List {
ForEach(self.timeCodeListVM.timeCodes) { timeCode in
TimeCodeDetailsCell(fullName: timeCode.fullName, abbreviation: timeCode.abbreviation, color: timeCode.color, isFavorite: timeCode.isFavorite, presentEditTimeCode: $presentEditTimeCode)
.contentShape(Rectangle())
.onTapGesture {
timeCodeEdit = timeCode
}
.sheet(item: $timeCodeEdit, onDismiss: didDismiss) { detail in
EditCodeView(timeCodeEdit: detail)
}
}
}
}
}
}
Here is the code for the View Models (shouldn't be relevant to the problem, but included for understanding):
class TimeCodeListViewModel: ObservableObject {
#Published var timeCodes = [TimeCodeViewModel]()
init() {
fetchAllTimeCodes()
}
func fetchAllTimeCodes() {
self.timeCodes = CoreDataManager.shared.getAllTimeCodes().map(TimeCodeViewModel.init)
}
}
class TimeCodeViewModel: Identifiable {
var id: String = ""
var fullName = ""
var abbreviation = ""
var color = ""
var isFavorite = false
var tags = ""
init(timeCode: TimeCode) {
self.id = timeCode.id!.uuidString
self.fullName = timeCode.fullName!
self.abbreviation = timeCode.abbreviation!
self.color = timeCode.color!
self.isFavorite = timeCode.isFavorite
self.tags = timeCode.tags!
}
}
Second Instance:
EDIT: I realize it may be difficult to understand what the code is doing, so I have included a gif demoing the problem (unfortunately I am not high enough reputation for it to be shown automatically). As you can see, I select the cells I want to change, then press the button to assign that TimeCode to it. The array of TimeCodeCellViewModels changes in the background, but you don't actually see that change until I press the home button and then reopen the app, which triggers a refresh of ForEach. Gif of issue. There is also this video if the GIF is too fast: https://imgur.com/a/Y5xtLJ3
I am trying to display a grid view using a VStack of HStacks, and am running into an issue where the ForEach I am using to display the content is not refreshing when the array being passed in changes. I know the array itself is changing because if I reduce it to a string and display the contents with Text(), it properly updates as soon as a change is made. But, the ForEach loop only updates if I close and reopen the app, forcing the ForEach to reload. I know that there is a special version of ForEach that is specifically designed for dynamic content, but I am pretty sure I am using this version since I pass in '''id: .self'''. Here is the main code snippet:
var hoursTimeCode: [[TimeCodeCellViewModel]] = []
// initialize hoursTimeCode
VStack(spacing: 3) {
ForEach(self.hoursTimeCode, id: \.self) {row in
HStack(spacing: 3){
HourTimeCodeCell(date: row[0].date) // cell view for hour
.frame(minWidth: 50)
ForEach(row.indices, id: \.self) {cell in
// TimeCodeBlockCell displays minutes normally. If it is selected, and a button is pressed, it is assigned a TimeCode which it will then display
TimeCodeBlockCell(timeCodeCellVM: row[cell], selectedArray: $selectedTimeCodeCells)
.frame(maxWidth: .infinity)
.aspectRatio(1.0, contentMode: .fill)
}
}
}
}
I'm pretty sure it doesn't change anything, but I did have to define a custom hash function for the TimeCodeCellViewModel, which might change the behavior of the ForEach (the attributes being changed are included in the hash function). However, I have noticed the same ForEach behavior in another part of my project that uses a different view model, so I highly doubt this is the issue.
class TimeCodeCellViewModel:Identifiable, Hashable {
static func == (lhs: TimeCodeCellViewModel, rhs: TimeCodeCellViewModel) -> Bool {
if lhs.id == rhs.id {
return true
}
else {
return false
}
}
func hash(into hasher: inout Hasher) {
hasher.combine(id)
hasher.combine(isSet)
hasher.combine(timeCode)
hasher.combine(date)
}
var id: String = ""
var date = Date()
var isSet = false
var timeCode: TimeCode
var frame: CGRect = .zero
init(timeCodeCell: TimeCodeCell) {
self.id = timeCodeCell.id!.uuidString
self.date = timeCodeCell.date!
self.isSet = timeCodeCell.isSet
self.timeCode = timeCodeCell.toTimeCode!
}
}
Here is a snippet of what you need to make the code work.
See the comments for some basics of why
struct EditCodeView:View{
#EnvironmentObject var timeCodeListVM: TimeCodeListViewModel
//This will observe changes to the view model
#ObservedObject var timeCodeViewModel: TimeCodeViewModel
var body: some View{
EditTimeCodeView(timeCode: timeCodeViewModel.timeCode)
.onDisappear(perform: {
//*********TO SEE CHANGES WHEN YOU EDIT
//uncomment this line***********
//_ = timeCodeListVM.update(timeCodeVM: timeCodeViewModel)
})
}
}
struct EditTimeCodeView: View{
//This will observe changes to the core data entity
#ObservedObject var timeCode: TimeCode
var body: some View{
Form{
TextField("name", text: $timeCode.fullName.bound)
TextField("appreviation", text: $timeCode.abbreviation.bound)
Toggle("favorite", isOn: $timeCode.isFavorite)
}
}
}
class TimeCodeListViewModel: ObservableObject {
//Replacing this whole thing with a #FetchRequest would be way more efficient than these extra view models
//IF you dont want to use #FetchRequest the only other way to observe the persistent store for changes is with NSFetchedResultsController
//https://stackoverflow.com/questions/67526427/swift-fetchrequest-custom-sorting-function/67527134#67527134
//This array will not see changes to the variables of the ObservableObjects
#Published var timeCodeVMs = [TimeCodeViewModel]()
private var persistenceManager = TimeCodePersistenceManager()
init() {
fetchAllTimeCodes()
}
func fetchAllTimeCodes() {
//This method does not observe for new and or deleted timecodes. It is a one time thing
self.timeCodeVMs = persistenceManager.retrieveObjects(sortDescriptors: nil, predicate: nil).map({
//Pass the whole object there isnt a point to just passing the variables
//But the way you had it broke the connection
TimeCodeViewModel(timeCode: $0)
})
}
func addNew() -> TimeCodeViewModel{
let item = TimeCodeViewModel(timeCode: persistenceManager.addSample())
timeCodeVMs.append(item)
//will refresh view because there is a change in count
return item
}
///Call this to save changes
func update(timeCodeVM: TimeCodeViewModel) -> Bool{
let result = persistenceManager.updateObject(object: timeCodeVM.timeCode)
//You have to call this to see changes at the list level
objectWillChange.send()
return result
}
}
//DO you have special code that you aren't including? If not what is the point of this view model?
class TimeCodeViewModel: Identifiable, ObservableObject {
//Simplify this
//This is a CoreData object therefore an ObservableObject it needs an #ObservedObject in a View so changes can be seem
#Published var timeCode: TimeCode
init(timeCode: TimeCode) {
self.timeCode = timeCode
}
}
Your first ForEach probably cannot check if the identity of Array<TimeCodeCellViewModel> has changed.
Perhaps you want to use a separate struct which holds internally an array of TimeCodeCellViewModel and conforms to Identifiable, effectively implementing such protocol.
stuct TCCViewModels: Identifiable {
let models: Array<TimeCodeCellViewModel>
var id: Int {
models.hashValue
}
}
You might as well make this generic too, so it can be reused for different view models in your app:
struct ViewModelsContainer<V: Identifiable> where V.ID: Hashable {
let viewModels: Array<V>
let id: Int
init(viewModels: Array<V>) {
self.viewModels = viewModels
var hasher = Hasher()
hasher.combine(viewModels.count)
viewModels.forEach { hasher.combine($0.id) }
self.id = hasher.finalize
}
}
I'm starting with SwiftUI and following WWDC videos I'm starting with #State and #Binding between two views. I got a display right, but don't get how to make back-forth read-write what was not include in WWDC videos.
I have model classes:
class Manufacturer {
let name: String
var models: [Model] = []
init(name: String, models: [Model]) {
self.name = name
self.models = models
}
}
class Model: Identifiable {
var name: String = ""
init(name: String) {
self.name = name
}
}
Then I have a drawing code to display that work as expected:
var body: some View {
VStack {
ForEach(manufacturer.models) { model in
Text(model.name).padding()
}
}.padding()
}
and I see this:
Canvas preview picture
But now I want to modify my code to allows editing this models displayed and save it to my model #Binding so I've change view to:
var body: some View {
VStack {
ForEach(self.$manufacturer.models) { item in
Text(item.name)
}
}.padding()
}
But getting and error in ForEach line:
Generic parameter 'ID' could not be inferred
What ID parameter? I'm clueless here... I thought Identifiable acting as identifier here.
My question is then:
I have one view (ContentView) that "holds" my datasource as #State variable. Then I'm passing this as #Binding to my ManufacturerView want to edit this in List with ForEach fill but cannot get for each binding working - how can I do that?
First, I'm assuming you have something like:
#ObservedObject var manufacturer: Manufacturer
otherwise you wouldn't have self.$manufacturer to begin with (which also requires Manufacturer to conform to ObservableObject).
self.$manufacturer.models is a type of Binding<[Model]>, and as such it's not a RandomAccessCollection, like self.manufacturer.models, which is one of the overloads that ForEach.init accepts.
And if you use ForEach(self.manufacturer.models) { item in ... }, then item isn't going to be a binding, which is what you'd need for, say, a TextField.
A way around that is to iterate over indices, and then bind to $manufacturer.models[index].name:
ForEach(manufacturer.indices) { index in
TextField("model name", self.$manufacturer.models[index].name)
}
In addition to that, I'd suggest you make Model (and possibly even Manufacturer) a value-type, since it appears to be just a storage of data:
struct Model: Identifiable {
var id: UUID = .init()
var name: String = ""
}
This isn't going to help with this problem, but it will eliminate possible issues with values not updating, since SwiftUI wouldn't detect a change.
Iam trying to use Picker as selection of struct. Let say I have a struct "Pet" like below
struct Pet: Identifiable, Codable, Hashable {
let id = UUID()
let name: String
let age: Int
}
I am getting all Pet's from some class, where Pets are defined as #Published var pets = Pet
static let pets = Class().pets
I would like to be able to write a selection from picker to below variable:
#State private var petSelection: Pet?
Picker is:
Picker("Pet", selection: $petSelection){
ForEach(Self.pets) { item in
Text(item.name)
}
}
Picker shows properly all avaliavble pets but when I chose one petSelection has been not changed (nil). How should I mange it?
Thanks!
Edit:
Of course I know that I can use tag like below:
Picker("Pet", selection: $petSelection) {
ForEach(0 ..< Self.pet.count) { index in
Text(Self.pet[index].name).tag(index)
}
But wonder is it possible to use struct as selection. Thanks
Short answer: The type associated with the tag of the entries in your Picker (the Texts) must be identical to the type used for storing the selection.
In your example: You have an optional selection (probably to allow "empty selection") of Pet?, but the array passed to ForEach is of type [Pet]. You have to add therefore a .tag(item as Pet?) to your entries to ensure the selection works.
ForEach(Self.pets) { item in
Text(item.name).tag(item as Pet?)
}
Here follows my initial, alternate answer (getting rid of the optionality):
You have defined your selection as an Optional of your struct: Pet?. It seems that the Picker cannot handle Optional structs properly as its selection type.
As soon as you get rid of the optional for example by introducing a "dummy/none-selected Pet", Picker starts working again:
extension Pet {
static let emptySelection = Pet(name: "", age: -1)
}
in your view initialise the selection:
#State private var petSelection: Pet = .emptySelection
I hope this helps you too.
You use the following way:
#Published var pets: [Pet?] = [ nil, Pet(name: "123", age: 23), Pet(name: "123dd", age: 243),]
VStack{
Text(petSelection?.name ?? "name")
Picker("Pet", selection: $petSelection){
ForEach(Self.pets, id: \.self) { item in
Text(item?.name ?? "name").tag(item)
}}}
the type of $petSelection in Picker(selection:[...] has to be the same type of id within your struct.
So in your case you would have to change $petSelection to type if UUID since your items within the collection have UUID as identifier.
Anyway since this is not what you're after, but your intention is to receive the Pet as a whole when selected. For that you will need a wrapper containing Pet as the id. Since Pet is already Identifiable, there're only a few adjustments to do:
Create a wrapper having Pet as an id
struct PetPickerItem {
let pet: Pet?
}
Now wrap all collection items within the picker item
Picker("Pet", selection: $petSelection) {
ForEach(Self.pets.map(PetPickerItem.init), id: \.pet) {
Text("\($0.pet?.name ?? "None")")
}
}
You can now do minor adjustments like making PetPickerItem identifiable to remove the parameter id: from ForEach.
That's the best solution I came up with.
This is how I do it:
struct Language: Identifiable, Hashable {
var title: String
var id: String
}
struct PickerView: View {
var languages: [Language] = [Language(title: "English", id: "en-US"), Language(title: "German", id: "de-DE"), Language(title: "Korean", id: "ko-KR")]
#State private var selectedLanguage = Language(title: "German", id: "de-DE")
var body: some View {
Picker(selection: $selectedLanguage, label: Text("Front Description")) {
ForEach(self.languages, id: \.self) {language in
Text(language.title)
}
}
}
I'm using an ObservableObject 'DataStore', which contains an array ('exampleList') of objects ('exampleObject').
#Published exampleList = [exampleObject]()
I'm calling the DataStore via #EnvironmentObject ('dataStore').
#EnvironmentObject var dataStore = DataStore()
Then I iterate the list with
ForEach(0..<dataStore.exampleList.count) { index in ....
To bind element of item to a detail view, I'm doing like this:
DetailView(itemBinding: $dataStore.exampleList[index])
Until Xcode11 beta 4, it worked perfectly. Since XCode11 beta 5, it still works but Xcode gives me this alert:
'subscript(_:)' is deprecated: See Release Notes for a migration path
I tried with simpler stuff, with a simple #State var containing an array of strings, and it's the same issue: when calling an element of this array, and trying to use the value into a TextField:
TextField("test", text: $test[0])
I get the same alert.
I don't understand how to fix it. Does that mean that we no longer can bind values inside an array?
Then, how can we iterate an array and bind a specific item?
This is my first question on Stack Overflow, I apologize if my question is clumsy...
Thanks a lot for your answers, I'm using Stack Overflow for years, it's amazing, I always find existing and helpful answers, but it is the first time I can't find any, that's why I'm asking.
Xcode 11, beta 6 UPDATE:
Good news! Just as I suspected, in beta 6, the Binding conformance to MutableCollection has been been replaced with something else. Instead of conforming to MutableCollection, it now let your access the elements via #dynamicMemberLookup. The result is you now can keep doing $text[3] and no longer get a warning! It seems this question can be closed now.
Xcode 11, beta 5. Old answer:
I finally got some time to investigate this a little. As I mentioned in the comments, I think it would be wise to wait until the Collection conformance is completely removed (or replaced with something else). But just to satisfy our curiosity, I have created an extension on Binding, that I think does what the current Collection conformance does. The only difference is that, instead of accessing through a subscript, I implemented a function called element(_ idx: Int) to get a Binding<T> to the element.
If one day the conformance is completely removed, I may change the implementation, and conform to Collection myself. I cannot do it now, because it would conflict with the existent (and deprecated) implementation. For the time being, I think this demonstrate how to handle the warnings if you absolutely want to get rid of them.
Just to be clear. I am not using this code. As long as I can still access the elements through the subscript, I will still do it and ignore the warnings. This is just for academic purposes.
The extension is:
extension Binding where Value: MutableCollection, Value.Index == Int {
func element(_ idx: Int) -> Binding<Value.Element> {
return Binding<Value.Element>(
get: {
return self.wrappedValue[idx]
}, set: { (value: Value.Element) -> () in
self.wrappedValue[idx] = value
})
}
}
And it can be used like this:
struct MainView: View {
#Binding var text: [String]
var body: some View {
TextField("", text: $text.element(0))
TextField("", text: $text.element(1))
TextField("", text: $text.element(2))
}
}
I had to bind the array of an observable object recently, didn't get any warnings on stable XCode11. I did it like this
struct ScheduleTimer: Identifiable {
var id: Int
var name: String
var start: Date
var end: Date
var isActive: Bool
}
struct ScheduleView: View {
#ObservedObject var scheduleController = ScheduleController()
var body: some View {
NavigationView {
Form {
ForEach(scheduleController.timers) { timer in
ScheduleForm(scheduleController: self.scheduleController, timer: timer)
}
}
}
}
}
struct ScheduleForm: View {
#ObservedObject var scheduleController: ScheduleController
var timer: ScheduleTimer
var scheduleIndex: Int {
scheduleController.timers.firstIndex(where: { $0.id == timer.id })!
}
#State var start = Date()
var body: some View {
Section(header: Text(self.scheduleController.timers[scheduleIndex].name)){
DatePicker("From", selection: self.$scheduleController.timers[scheduleIndex].start, displayedComponents: .hourAndMinute)
DatePicker("To", selection: self.$scheduleController.timers[scheduleIndex].end, displayedComponents: .hourAndMinute)
Toggle(isOn: self.$scheduleController.timers[scheduleIndex].isActive) {
Text("")
}.toggleStyle(DefaultToggleStyle())
}
}
}
class ScheduleController: ObservableObject {
#Published var timers = [ScheduleTimer]()
...