The navigationDestination is being called a single time when using an array of type (ie: [String]) but multiple times when using NavigationPath after an append.
Check it with a breakpoint on Text(string) and switching the path types.
iOS 16.1 / Xcode 14.0 and 14.1
import SwiftUI
struct ContentView: View {
#State private var path = NavigationPath()
// #State private var path = [String]()
var body: some View {
NavigationStack(path: $path) {
VStack {
Button("append") {
path.append("string")
}
}
.navigationDestination(for: String.self) { string in
Text(string) // <--- breakpoint here
}
}
}
}
This is a workaround suggest by the Apple DTS engineer that may be useful (does not solve all cases depending on your navigation/views structure).
import SwiftUI
struct Model: Hashable {
var intValue: Int
var stringValue: String
init(_ value: Int) {
intValue = value
stringValue = value.description
}
}
struct ContentView: View {
#State private var path = NavigationPath()
#State private var models: [Int: Model] = [:]
var body: some View {
NavigationStack(path: $path) {
VStack {
Button("append") {
path.append(Int.random(in: 0...100))
}
}
.navigationDestination(for: Int.self) { int in
let model = model(for: int)
Text(model.stringValue)
}
}
}
func model(for int: Int) -> Model {
if let string = models[int] {
return string // <--- breakpoint here
} else {
let model = Model(int)
models[int] = model
return model // <--- breakpoint here
}
}
}
Related
I'm having issues pulling data from an Array into a picker using SwiftUI. I can correctly make a list of the data I'm interested in, but can't seem to make the same logic work to pull the data into a picker. I've coded it a few different ways but the current way I have gives this error:
Referencing initializer 'init(_:content:)' on 'ForEach' requires that 'Text' conform to 'TableRowContent'
The code is below:
import SwiftUI
struct BumpSelector: View {
#ObservedObject var model = ViewModel()
#State var selectedStyle = 0
init(){
model.getData2()}
var body: some View {
VStack{
List (model.list) { item in
Text(item.style)}
Picker("Style", selection: $selectedStyle, content: {
ForEach(0..<model.list.count, content: { index in
Text(index.style)
})
})
}
}
The model is here:
import Foundation
struct Bumps: Identifiable{
var id: String
var style: String
}
and the ViewModel is here:
import Foundation
import Firebase
import FirebaseFirestore
class ViewModel: ObservableObject {
#Published var list = [Bumps]()
#Published var styleArray = [String]()
func getData2() {
let db = Firestore.firestore()
db.collection("bumpStop").getDocuments { bumpSnapshot, error in
//Check for errors first:
if error == nil {
//Below ensures bumpSnapshot isn't nil
if let bumpSnapshot = bumpSnapshot {
DispatchQueue.main.async {
self.list = bumpSnapshot.documents.map{ bump in
return Bumps(id: bump.documentID,
style: bump["style"] as? String ?? "")
}
}
}
}
else {
//Take care of the error
}
}
}
}
index in your ForEach is just an Int, there is no style associated with an Int. You could try this approach to make the Picker work with its ForEach:
struct BumpSelector: View {
#ObservedObject var model = ViewModel()
#State var selectedStyle = 0
init(){
model.getData2()
}
var body: some View {
VStack{
List (model.list) { item in
Text(item.style)}
Picker("Style", selection: $selectedStyle) {
ForEach(model.list.indices, id: \.self) { index in
Text(model.list[index].style).tag(index)
}
}
}
}
}
EDIT-1:
Text(model.list[selectedStyle].style) will give you the required style of the selectedStyle.
However, as always when using index, you need to ensure it is valid at the time of use.
That is, use if selectedStyle < model.list.count { Text(model.list[selectedStyle].style) }.
You could also use this alternative approach that does not use index:
struct Bumps: Identifiable, Hashable { // <-- here
var id: String
var style: String
}
struct BumpSelector: View {
#ObservedObject var model = ViewModel()
#State var selectedBumps = Bumps(id: "", style: "") // <-- here
init(){
model.getData2()
}
var body: some View {
VStack{
List (model.list) { item in
Text(item.style)
}
Picker("Style", selection: $selectedBumps) {
ForEach(model.list) { bumps in
Text(bumps.style).tag(bumps) // <-- here
}
}
}
.onAppear {
if let first = model.list.first {
selectedBumps = first
}
}
}
}
Then use selectedBumps, just like any Bumps, such as selectedBumps.style
I'm currently developing an application using SwiftUI.
I want to use a UserDefaults value in this app.
So I made a code below.
But in this case, when I reboot the app(the 4'th process in the process below), I can't get value from UserDefaults...
Build and Run this project.
Pless the home button and the app goes to the background.
Double-tap the home button and remove the app screen.
press the app icon and reboot the app. Then I want to get value from UserDefaults.
to resolve this problem how should I set and get a value in UserDefaults?
Here is the code:
import SwiftUI
struct ContentView: View {
#State var text = "initialText"
var body: some View {
VStack {
Text(text)
TextField( "", text: $text)
}.onAppear(){
if let text = UserDefaults.standard.object(forKey: "text" ){
self.text = text as! String
}
}
.onDisappear(){
UserDefaults.standard.set(self.text, forKey: "text")
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
ADD
When I add this class following the first answer, that code has a couple of errors like this, is it usual?
Xcode: Version 11.7
Swift: Swift 5
Set in a class like this your values: Bool, String(see example), Int, etc...
#if os(iOS)
import UIKit
#else
import AppKit
#endif
import Combine
#propertyWrapper struct UserDefault<T> {
let key: String
let defaultValue: T
init(_ key: String, defaultValue: T) {
self.key = key
self.defaultValue = defaultValue
}
var wrappedValue: T {
get {
return UserDefaults.standard.object(forKey: key) as? T ?? defaultValue
}
set {
UserDefaults.standard.set(newValue, forKey: key)
}
}
}
final class UserSettings: ObservableObject {
let objectWillChange = PassthroughSubject<Void, Never>()
#UserDefault("myText", defaultValue: "initialText")
var myText: String {
willSet { objectWillChange.send() }
}
}
this to read:
let settings = UserSettings()
let count = settings.countSentence // default countsentence 1
this to update:
let settings = UserSettings()
settings.countSentence = 3 // default countsentence 3
Based on your code:
struct ContentView: View {
let UserDef = UserSettings()
#State var text = ""
var body: some View {
VStack {
Text(UserDef.myText)
TextField("placeholder", text: $text, onCommit: { self.UserDef.myText = self.text})
}.onAppear() {
self.text = self.UserDef.myText
}
}
}
I'm trying to fill up a Picker with data fetched asynchronously from external API.
This is my model:
struct AppModel: Identifiable {
var id = UUID()
var appId: String
var appBundleId : String
var appName: String
var appSKU: String
}
The class that fetches data and publish is:
class AppViewModel: ObservableObject {
private var appStoreProvider: AppProvider? = AppProvider()
#Published private(set) var listOfApps: [AppModel] = []
#Published private(set) var loading = false
fileprivate func fetchAppList() {
self.loading = true
appStoreProvider?.dataProviderAppList { [weak self] (appList: [AppModel]) in
guard let self = self else {return}
DispatchQueue.main.async() {
self.listOfApps = appList
self.loading = false
}
}
}
init() {
fetchAppList()
}
}
The View is:
struct AppView: View {
#ObservedObject var appViewModel: AppViewModel = AppViewModel()
#State private var selectedApp = 0
var body: some View {
ActivityIndicatorView(isShowing: self.appViewModel.loading) {
VStack{
// The Picker doesn't bind with appViewModel
Picker(selection: self.$selectedApp, label: Text("")) {
ForEach(self.appViewModel.listOfApps){ app in
Text(app.appName).tag(app.appName)
}
}
// The List correctly binds with appViewModel
List {
ForEach(self.appViewModel.listOfApps){ app in
Text(app.appName.capitalized)
}
}
}
}
}
}
While the List view binds with the observed object appViewModel, the Picker doesn't behave in the same way. I can't realize why. Any help ?
I filed bug report, FB7670992. Apple responded yesterday, suggesting that I confirm this behavior in iOS 14, beta 1. It appears to now have been resolved.
struct ContentView: View {
#ObservedObject var viewModel = ViewModel()
var body: some View {
Picker("", selection: $viewModel.wheelPickerValue) {
ForEach(viewModel.objects) { object in
Text(object.string)
}
}
.pickerStyle(WheelPickerStyle())
.labelsHidden()
}
}
Where
struct Object: Identifiable {
let id = UUID().uuidString
let string: String
}
class ViewModel: ObservableObject {
private var counter = 0
#Published private(set) var objects: [Object] = []
#Published var segmentedPickerValue: String = ""
#Published var wheelPickerValue: String = ""
fileprivate func nextSetOfValues() {
let newCounter = counter + 3
objects = (counter..<newCounter).map { value in Object(string: "\(value)") }
let id = objects.first?.id ?? ""
segmentedPickerValue = id
wheelPickerValue = id
counter = newCounter
}
init() {
let timer = Timer.scheduledTimer(withTimeInterval: 2, repeats: true) { [weak self] timer in
guard let self = self else { timer.invalidate(); return }
self.nextSetOfValues()
}
timer.fire()
}
}
Results in:
I can't put this into your code because it is incomplete but here is a sample.
Pickers aren't meant to be dynamic. They have to be completely reloaded.
class DynamicPickerViewModel: ObservableObject {
#Published private(set) var listOfApps: [YourModel] = []
#Published private(set) var loading = false
fileprivate func fetchAppList() {
loading = true
DispatchQueue.main.async() {
self.listOfApps.append(YourModel.addSample())
self.loading = false
}
}
init() {
fetchAppList()
}
}
struct DynamicPicker: View {
#ObservedObject var vm = DynamicPickerViewModel()
#State private var selectedApp = ""
var body: some View {
VStack{
//Use your loading var to reload the picker when it is done
if !vm.loading{
//Picker is not meant to be dynamic, it needs to be completly reloaded
Picker(selection: self.$selectedApp, label: Text("")) {
ForEach(self.vm.listOfApps){ app in
Text(app.name!).tag(app.name!)
}
}
}//else - needs a view while the list is being loaded/loading = true
List {
ForEach(self.vm.listOfApps){ app in
Text(app.name!.capitalized)
}
}
Button(action: {
self.vm.fetchAppList()
}, label: {Text("fetch")})
}
}
}
struct DynamicPicker_Previews: PreviewProvider {
static var previews: some View {
DynamicPicker()
}
}
Im trying to create an environment object that is editable and putting it in a list.
The Variables are only refreshing when I switch the tab for example (so whenever I leave the NavigationView) and then come back.
The same worked with a ModalView before. Is it a bug maybe? Or am I doing something wrong?
import SwiftUI
import Combine
struct TestView: View {
#State var showSheet: Bool = false
#EnvironmentObject var feed: TestObject
func addObjects() {
var strings = ["one","two","three","four","five","six"]
for s in strings {
var testItem = TestItem(text: s)
self.feed.items.append(testItem)
}
}
var body: some View {
TabView {
NavigationView {
List(feed.items.indices, id:\.self) { i in
NavigationLink(destination: detailView(feed: self._feed, i: i)) {
HStack {
Text(self.feed.items[i].text)
Text("(\(self.feed.items[i].read.description))")
}
}
}
}
.tabItem({ Text("Test") })
.tag(0)
Text("Blank")
.tabItem({ Text("Test") })
.tag(0)
}.onAppear {
self.addObjects()
}
}
}
struct detailView: View {
#EnvironmentObject var feed: TestObject
var i: Int
var body: some View {
VStack {
Text(feed.items[i].text)
Text(feed.items[i].read.description)
Button(action: { self.feed.items[self.i].isRead.toggle() }) {
Text("Toggle read")
}
}
}
}
final class TestItem: ObservableObject {
init(text: String) {
self.text = text
self.isRead = false
}
static func == (lhs: TestItem, rhs: TestItem) -> Bool {
lhs.text < rhs.text
}
var text: String
var isRead: Bool
let willChange = PassthroughSubject<TestItem, Never>()
var read: Bool {
set {
self.isRead = newValue
}
get {
self.isRead
}
}
}
class TestObject: ObservableObject {
var willChange = PassthroughSubject<TestObject, Never>()
#Published var items: [TestItem] = [] {
didSet {
willChange.send(self)
}
}
}
try passing .environmentObject on your destination:
NavigationLink(destination: detailView(feed: self._feed, i: i).environmentObject(x))
You have to use willSet instead of didSet.
TestItem should be a value type: struct or enum. SwiftUI's observation system properly works only with value types.
My code is a little more complex than this so I created an example that gets the same error.
When I navigate into a view, I have a function I want to perform with a variable passed into this view. That function then produces an array. I then want to put that array into a List, but I get an error.
How do I get the List to show the produced array?
I think the issue is the List can't be updated because it already has the declared blank array.
struct ContentView : View {
#State var array = [String]()
var body: some View {
List(self.array,id: \.self) { item in
Text("\(item)")
}
.onAppear(perform: createArrayItems)
}
func createArrayItems() {
array = ["item1", "item2", "item3", "item4", "item5"]
}
}
You can use ObservableObject data providers(eg : ViewModel) with #Published properties.
struct ListView: View {
#ObservedObject var viewModel = ListViewModel()
var body: some View {
NavigationView {
List(){
ForEach(viewModel.items) { item in
Text(item)
}
}
}
}
}
#if DEBUG
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ListView()
}
}
#endif
class ListViewModel: ObservableObject {
#Published var items = ["item1", "item2", "item3", "item4", "item5","item6"]
func addItem(){
items.append("item7")
}
}
You can use combine framework to update the list.
Whenever a change is made in DataProvider Object it will automatically update the list.
struct ContentView : View {
#EnvironmentObject var data: DataProvider
var body: some View {
NavigationView {
NavigationButton(destination: SecondPage()) {
Text("Go to Second Page")
}
List {
ForEach(data.array.identified(by: \.self)) { item in
Text("\(item)")
}
}
}
}
}
Add items in the list
struct SecondPage : View {
#State var counter = 1
#EnvironmentObject var tempArray: DataProvider
var body: some View {
VStack {
Button(action: {
self.tempArray.array.append("item\(self.counter)")
self.counter += 1
}) {
Text("Add items")
}
Text("Number of items added \(counter-1)")
}
}
}
It will simply notify the change
import Combine
final class DataProvider: BindableObject {
let didChange = PassthroughSubject<DataProvider, Never>()
var array = [String]() {
didSet {
didChange.send(self)
}
}
}
You also need to do some update in the SceneDelegate. This update ensures that ContentView has a DataProvider object in the environment.
window.rootViewController = UIHostingController(rootView: ContentView().environmentObject(DataProvider()))
#txagPman
I too have your problem to understand how to modify a list.
I was able to write this code.
I hope it's useful.
import SwiftUI
struct ContentView: View {
#State private var array = createArrayItems()
// #State private var array = [""] - This work
// #State private var array = [] - This not work
#State private var text = ""
var body: some View {
VStack {
TextField("Text", text: $text, onCommit: {
// self.array = createArrayItems() - This work after press return on textfield
self.array.append(self.text)
}).padding()
List (self.array, id: \.self) {item in
Text("\(item)")
}
}
// .onAppear {
// self.array = createArrayItems() - This not work
// }
}
}
func createArrayItems() -> [String] {
return ["item_01","item_02","item_03","item_04" ]
}
A dumb UI is a good UI
Keep your views dumb try the following code to create a dynamic List
import UIKit
import SwiftUI
import PlaygroundSupport
struct ContentView : View {
#State var array = [String]()
var body: some View {
List{
ForEach(array.identified(by: \.self)) { item in
Text("\(item)")
}
}
}
}
func createArrayItems()->[String] {
return ["item1", "item2", "item3", "item4", "item5","item6"]
}
PlaygroundPage.current.liveView = UIHostingController(rootView: ContentView(array: createArrayItems()))
Use this:
class ObservableArray<T>: ObservableObject {
#Published var array: [T]
init(array: [T] = ) {
self.array = array
}
init(repeating value: T, count: Int) {
array = Array(repeating: value, count: count)
}
}
struct YourView: View {
#ObservedObject var array = ObservableArray<String>()
var body: some View {
}
}