I tried to build a form that contained multiple picker. The first picker will show the existing data. The second picker will get the data from API according to the selection from first picker. However, when I open the form, the first picker work but the second picker display nothing. Even I select other selection from first picker, I can get the data but the second picker didn't update as my expectation. So the main question is how to make the second picker get data since there is a default selection in first picker. And what is the problem that cause the second picker no update after I make a selection in first picker
struct addBooking : View {
#State var shops = ShopJSON.shared.shops //existing data
#State var selectedShopIndex = 0
#State var selectedOutletIndex = 0
#ObservedObject var bookingOutletJSON = BookingOutletJSON()
var body: some View {
NavigationView{
Form {
Picker(selection: $selectedShopIndex, label: Text("Select Shop")) {
ForEach(0 ..< shops.count) {
Text(self.shops[$0].name!)
}
}
.onChange(of: selectedShopIndex, perform: { (value) in
print("Shop changed")
bookingOutletJSON.getOutlet(selectedShopId: shops[value].shopID!)
})
Picker(selection: $selectedOutletIndex, label: Text("Select Outlet")){
ForEach(0 ..< bookingOutletJSON.outlets.count) {
Text(self.bookingOutletJSON.outlets[$0].location!)
}
}
if bookingOutletJSON.outlets.count != 0 {
Text("\(bookingOutletJSON.outlets[0].location!)")
}
class BookingOutletJSON : ObservableObject{
#Published var outlets = [BookingOutlets]()
init() {
}
func getOutlet(selectedShopId : Int){
//API get data
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard let data = data else {
print(String(describing: error))
return
}
if let decodedOutlet = try? JSONDecoder().decode(OutletModal.self, from: data) {
DispatchQueue.main.async {
self.outlets = decodedOutlet.outlets!
print(self.outlets)
print("Outlet updated")
}
} else {
print("Invalid response from server")
}
}
task.resume()
}
}
Try with another ForEach constructor
Picker(selection: $selectedOutletIndex, label: Text("Select Outlet")){
ForEach(bookingOutletJSON.outlets.indices, id: \.self) {
Text(self.bookingOutletJSON.outlets[$0].location!)
}
}
Related
I am trying to write a "Single View App" in SwiftUI. The main design is very simple. I have a list of items (say Expense) which I am displaying in main view in NavigationView -> List.
List View Source Code
import SwiftUI
struct AmountBasedModifier : ViewModifier{
var amount: Int
func body(content: Content) -> some View {
if amount <= 10{
return content.foregroundColor(Color.green)
}
else if amount <= 100{
return content.foregroundColor(Color.blue)
}
else {
return content.foregroundColor(Color.red)
}
}
}
extension View {
func amountBasedStyle(amount: Int) -> some View {
self.modifier(AmountBasedModifier(amount: amount))
}
}
struct ExpenseItem: Identifiable, Codable {
var id = UUID()
var name: String
var type: String
var amount: Int
static var Empty: ExpenseItem{
return ExpenseItem(name: "", type: "", amount: 0)
}
}
class Expenses: ObservableObject {
#Published var items = [ExpenseItem](){
didSet{
let encoder = JSONEncoder()
if let data = try? encoder.encode(items){
UserDefaults.standard.set(data, forKey: "items")
}
}
}
init() {
let decoder = JSONDecoder()
if let data = UserDefaults.standard.data(forKey: "items"){
if let items = try? decoder.decode([ExpenseItem].self, from: data){
self.items = items
return
}
}
items = []
}
}
struct ContentView: View {
#ObservedObject var expenses = Expenses()
#State private var isShowingAddNewItemView = false
var body: some View {
NavigationView{
List{
ForEach(self.expenses.items) { item in
NavigationLink(destination: ExpenseItemHost(item: item, expenses: self.expenses)){
HStack{
VStack(alignment: .leading){
Text(item.name)
.font(.headline)
Text(item.type)
.font(.subheadline)
}
Spacer()
Text("$\(item.amount)")
.amountBasedStyle(amount: item.amount)
}
}
}.onDelete(perform: removeItems)
}
.navigationBarTitle("iExpense")
.navigationBarItems(leading: EditButton(), trailing: Button(action:
{
self.isShowingAddNewItemView.toggle()
}, label: {
Image(systemName: "plus")
}))
.sheet(isPresented: $isShowingAddNewItemView) {
AddNewExpense(expenses: self.expenses)
}
}
}
func removeItems(at offsets: IndexSet){
self.expenses.items.remove(atOffsets: offsets)
}
}
Each row item is NavigationLink that opens the Expense in readonly mode showing all the attributes of Expense Item.
There is an Add button at the top right to let user add a new expense item in list. The AddNewExpenseView (shown as sheet) has access to the list data source. So whenever user adds an new expense then data source of list is updated (by appending new item) and the sheet is dismissed.
Add View Source Code
struct AddNewExpense: View {
#ObservedObject var expenses: Expenses
#Environment(\.presentationMode) var presentationMode
#State private var name = ""
#State private var type = "Personal"
#State private var amount = ""
#State private var isShowingAlert = false
static private let expenseTypes = ["Personal", "Business"]
var body: some View {
NavigationView{
Form{
TextField("Name", text: $name)
Picker("Expense Type", selection: $type) {
ForEach(Self.expenseTypes, id: \.self) {
Text($0)
}
}
TextField("Amount", text: $amount)
}.navigationBarTitle("Add New Expense", displayMode: .inline)
.navigationBarItems(trailing: Button(action: {
if let amount = Int(self.amount){
let expenseItem = ExpenseItem(name: self.name, type: self.type, amount: amount)
self.expenses.items.append(expenseItem)
self.presentationMode.wrappedValue.dismiss()
}else{
self.isShowingAlert.toggle()
}
}, label: {
Text("Save")
}))
.alert(isPresented: $isShowingAlert) {
Alert.init(title: Text("Invalid Amount"), message: Text("The amount should only be numbers and without decimals"), dismissButton: .default(Text("OK")))
}
}
}
}
Expense Detail (Read Only) View Source Code
struct ExpenseItemView: View {
var item: ExpenseItem
var body: some View {
List{
Section{
Text("Name")
.font(.headline)
Text(item.name)
}
Section{
Text("Expense Type")
.font(.headline)
Text(item.type)
}
Section{
Text("Amount")
.font(.headline)
Text("$\(item.amount)")
}
}.listStyle(GroupedListStyle())
.navigationBarTitle(Text("Expense Details"), displayMode: .inline)
}
}
So far everything good. I then thought of adding an Edit button on the ExpenseItem View screen so that user can edit the Expense. I created an edit View which is launched as a sheet from ReadOnly View when Edit button is clicked.
Edit View Code
struct ExpenseItemHost: View {
#State var isShowingEditSheet = false
#State var item: ExpenseItem
#State var itemUnderEdit = ExpenseItem.Empty
var expenses: Expenses
var body: some View {
VStack{
ExpenseItemView(item: self.item)
}
.navigationBarItems(trailing: Button("Edit")
{
self.isShowingEditSheet.toggle()
})
.sheet(isPresented: $isShowingEditSheet) {
EditExpenseItemView(item: self.$itemUnderEdit)
.onAppear(){
self.itemUnderEdit = self.item
}
.onDisappear(){
//TO DO: Handle the logic where save is done when user has explicitly pressed "Done" button. `//Presently it is saving even if Cancel button is clicked`
if let indexAt = self.expenses.items.firstIndex( where: { listItem in
return self.item.id == listItem.id
}){
self.expenses.items.remove(at: indexAt)
}
self.item = self.itemUnderEdit
self.expenses.items.append(self.item)
}
}
}
}
struct EditExpenseItemView: View {
#Environment(\.presentationMode) var presentationMode
#Binding var item: ExpenseItem
static private let expenseTypes = ["Personal", "Business"]
var body: some View {
NavigationView{
Form{
TextField("Name", text: self.$item.name)
Picker("Expense Type", selection: self.$item.type) {
ForEach(Self.expenseTypes, id: \.self) {
Text($0)
}
}
TextField("Amount", value: self.$item.amount, formatter: NumberFormatter())
}
.navigationBarTitle(Text(""), displayMode: .inline)
.navigationBarItems(leading: Button("Cancel"){
self.presentationMode.wrappedValue.dismiss()
}, trailing: Button("Done"){
self.presentationMode.wrappedValue.dismiss()
})
}
}
}
Screenshots
Problem
I expect that when user is done with editing by pressing Done button the Sheet should come back to ReadOnly screen as this is where user clicked Edit button. But since I am modifying the data source of ListView when Done button is clicked so the ListView is getting recreated/refreshed. So instead of EditView sheet returning to ReadOnly view, the ListView is getting displayed when Done button is clicked.
Since my code is changing the data source of a view which is right now not accessible to user so below exception is also getting generated
2020-08-02 19:30:11.561793+0530 iExpense[91373:6737004] [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). This may cause bugs by forcing views inside the table view to load and perform layout without accurate information (e.g. table view bounds, trait collection, layout margins, safe area insets, etc), and will also cause unnecessary performance overhead due to extra layout passes. Make a symbolic breakpoint at UITableViewAlertForLayoutOutsideViewHierarchy to catch this in the debugger and see what caused this to occur, so you can avoid this action altogether if possible, or defer it until the table view has been added to a window. Table view: <_TtC7SwiftUIP33_BFB370BA5F1BADDC9D83021565761A4925UpdateCoalescingTableView: 0x7f9a8b021800; baseClass = UITableView; frame = (0 0; 414 896); clipsToBounds = YES; autoresize = W+H; gestureRecognizers = <NSArray: 0x6000010a1110>; layer = <CALayer: 0x600001e8c0e0>; contentOffset: {0, -140}; contentSize: {414, 220}; adjustedContentInset: {140, 0, 34, 0}; dataSource: <_TtGC7SwiftUIP13$7fff2c9a5ad419ListCoreCoordinatorGVS_20SystemListDataSourceOs5Never_GOS_19SelectionManagerBoxS2___: 0x7f9a8a5073f0>>
I can understand why ListView refresh is getting triggered but what I could not figure out is the correct pattern to edit the model as well as not cause the ListView refresh to trigger when we have intermediate screen in between i.e. List View -> ReadOnly -> Edit View.
What is the suggestion to handle this case?
Consider the following project with two views. The first view presents the second one:
import SwiftUI
struct ContentView: View {
private let data = 0...1000
#State private var selection: Set<Int> = []
#State private var shouldShowSheet = false
var body: some View {
self.showSheet()
//self.showPush()
}
private func showSheet() -> some View {
Button(action: {
self.shouldShowSheet = true
}, label: {
Text("Selected: \(selection.count) items")
}).sheet(isPresented: self.$shouldShowSheet) {
EditFormView(selection: self.$selection)
}
}
private func showPush() -> some View {
NavigationView {
Button(action: {
self.shouldShowSheet = true
}, label: {
NavigationLink(destination: EditFormView(selection: self.$selection),
isActive: self.$shouldShowSheet,
label: {
Text("Selected: \(selection.count) items")
})
})
}
}
}
struct EditFormView: View {
private let data = 0...1000
#Binding var selection: Set<Int>
#State private var editMode: EditMode = .active
init(selection: Binding<Set<Int>>) {
self._selection = selection
}
var body: some View {
List(selection: self.$selection) {
ForEach(data, id: \.self) { value in
Text("\(value)")
}
}.environment(\.editMode, self.$editMode)
}
}
Steps to reproduce:
Create an app with the above two views
Run the app and present the sheet with the editable list
Select some items at random indexes, for example a handful at index 0-10 and another handful at index 90-100
Close the sheet by swiping down/tapping back button
Open the sheet again
Scroll to indexes 90-100 to view the selection in the reused cells
Expected:
The selected indexes as you had will be in “selected state”
Actual:
The selection you had before is not marked as selected in the UI, even though the binding passed to List contains those indexes.
This occurs both on the “sheet” presentation and the “navigation link” presentation.
If you select an item in the list, the “redraw” causes the original items that were originally not shown as selected to now be shown as selected.
Is there a way around this?
It looks like EditMode bug, worth submitting feedback to Apple. The possible solution is to use custom selection feature.
Here is a demo of approach (modified only part). Tested & worked with Xcode 11.4 / iOS 13.4
struct EditFormView: View {
private let data = 0...1000
#Binding var selection: Set<Int>
init(selection: Binding<Set<Int>>) {
self._selection = selection
}
var body: some View {
List(selection: self.$selection) {
ForEach(data, id: \.self) { value in
self.cell(for: value)
}
}
}
// also below can be separated into standalone view
private func cell(for value: Int) -> some View {
let selected = self.selection.contains(value)
return HStack {
Image(systemName: selected ? "checkmark.circle" : "circle")
.foregroundColor(selected ? Color.blue : nil)
.font(.system(size: 24))
.onTapGesture {
if selected {
self.selection.remove(value)
} else {
self.selection.insert(value)
}
}.padding(.trailing, 8)
Text("\(value)")
}
}
}
Scenario:
I have a simple picker within a form.
I select a picker item (with chevron) from the form row.
I choose an item (row) from a list of items in the result panel.
The result panel slides away to reveal the original panel.
I am NOT able to repeat this procedure.
Here's my code:
class ChosenView: ObservableObject {
static let choices = ["Modal", "PopOver", "Circle", "CircleImage", "Scroll", "Segment", "Tab", "Multi-Line"]
#Published
var type = 0
}
struct ContentView: View {
#ObservedObject var chosenView = ChosenView()
#State private var isPresented = false
var body: some View {
VStack {
NavigationView {
Form {
Picker(selection: $chosenView.type, label: Text("The Panels")) {
ForEach(0..<ChosenView.choices.count) {
Text(ChosenView.choices[$0]).tag($0)
}
}
}.navigationBarTitle(Text("Available Views"))
.actionSheet(isPresented: $isPresented, content: {
ActionSheet(title: Text("Hello"))
})
}
Section {
Button(action: launchView) {
Text("Select: \(ChosenView.choices[chosenView.type])")
}
}
Spacer()
}
}
private func launchView() {
isPresented = true
}
}
What am I missing?
Why can't I repeat picker selection rather than having to reboot?
I have a Picker Element in a VStack, but when its content changes by adding a new Element, the Picker does not refresh.
After hiding and showing the Picker, the new Element is visible.
Does anybody have any idea how to refresh the content of a Picker, without needing to hide / show it?
You can reproduce this by creating a new SwiftUI project and copying the following code instead of the "ContentView" struct.
class ContentModel {
#Published var pickerData: [String] = ["1"]
func addPickerData() {
pickerData.append("\(pickerData.count + 1)")
}
}
struct ContentView: View {
let contentModel = ContentModel()
#State private var showPicker = false
#State private var selectedPickerValue = ""
var body: some View {
VStack(spacing: 8) {
Text("Adding a new Element to the Picker does not refresh its content :-(")
Button(action: {
self.contentModel.addPickerData()
}) {
Text("Add Picker Data")
}
Button(action: {
self.showPicker.toggle()
}) {
Text("Show / Hide 2nd Picker")
}
Picker("Select",selection: $selectedPickerValue) {
ForEach(contentModel.pickerData, id: \.self) { data in
Text(data)
}
}
if (showPicker) {
Picker("Select",selection: $selectedPickerValue) {
ForEach(contentModel.pickerData, id: \.self) { data in
Text(data)
}
}
}
Text("Selected Value: \(selectedPickerValue)")
}
}
}
Thanks in advance for any help!
Here is the trick of reactive and always use two copies of same thing when you need to refresh something.
class ContentModel{
#Published var pickerData: [String] = ["1"]
func addPickerData() {
pickerData.append("\(pickerData.count + 1)")
}
}
struct ContentSSView: View {
let contentModel = ContentModel()
#State private var showPicker = false
#State private var selectedPickerValue = ""
var body: some View {
VStack(spacing: 8) {
Text("Adding a new Element to the Picker does not refresh its content :-(")
Button(action: {
self.contentModel.addPickerData()
self.showPicker.toggle()
}) {
Text("Add Picker Data")
}
Button(action: {
self.showPicker.toggle()
}) {
Text("Show / Hide 2nd Picker")
}
if (showPicker) {
Picker("Select",selection: $selectedPickerValue) {
ForEach(contentModel.pickerData, id: \.self) { data in
Text(data)
}
}
}else{
Picker("Select",selection: $selectedPickerValue) {
ForEach(contentModel.pickerData, id: \.self) { data in
Text(data)
}
}
}
Text("Selected Value: \(selectedPickerValue)")
}
}
}
I have a GitHub repo with this issue. I don't think having two Pickers is a viable solution.
Picker Update Bug GitHub Repo
I want to change another unrelated #State variable when a Picker gets changed, but there is no onChanged and it's not possible to put a didSet on the pickers #State. Is there another way to solve this?
Deployment target of iOS 14 or newer
Apple has provided a built in onChange extension to View, which can be used like this:
struct MyPicker: View {
#State private var favoriteColor = 0
var body: some View {
Picker(selection: $favoriteColor, label: Text("Color")) {
Text("Red").tag(0)
Text("Green").tag(1)
}
.onChange(of: favoriteColor) { tag in print("Color tag: \(tag)") }
}
}
Deployment target of iOS 13 or older
struct MyPicker: View {
#State private var favoriteColor = 0
var body: some View {
Picker(selection: $favoriteColor.onChange(colorChange), label: Text("Color")) {
Text("Red").tag(0)
Text("Green").tag(1)
}
}
func colorChange(_ tag: Int) {
print("Color tag: \(tag)")
}
}
Using this helper
extension Binding {
func onChange(_ handler: #escaping (Value) -> Void) -> Binding<Value> {
return Binding(
get: { self.wrappedValue },
set: { selection in
self.wrappedValue = selection
handler(selection)
})
}
}
First of all, full credit to ccwasden for the best answer. I had to modify it slightly to make it work for me, so I'm answering this question hoping someone else will find it useful as well.
Here's what I ended up with (tested on iOS 14 GM with Xcode 12 GM)
struct SwiftUIView: View {
#State private var selection = 0
var body: some View {
Picker(selection: $selection, label: Text("Some Label")) {
ForEach(0 ..< 5) {
Text("Number \($0)") }
}.onChange(of: selection) { _ in
print(selection)
}
}
}
The inclusion of the "_ in" was what I needed. Without it, I got the error "Cannot convert value of type 'Int' to expected argument type '()'"
I think this is simpler solution:
#State private var pickerIndex = 0
var yourData = ["Item 1", "Item 2", "Item 3"]
// USE this if needed to notify parent
#Binding var notifyParentOnChangeIndex: Int
var body: some View {
let pi = Binding<Int>(get: {
return self.pickerIndex
}, set: {
self.pickerIndex = $0
// TODO: DO YOUR STUFF HERE
// TODO: DO YOUR STUFF HERE
// TODO: DO YOUR STUFF HERE
// USE this if needed to notify parent
self.notifyParentOnChangeIndex = $0
})
return VStack{
Picker(selection: pi, label: Text("Yolo")) {
ForEach(self.yourData.indices) {
Text(self.yourData[$0])
}
}
.pickerStyle(WheelPickerStyle())
.padding()
}
}
I know this is a year old post, but I thought this solution might help others that stop by for a visit in need of a solution. Hope it helps someone else.
import Foundation
import SwiftUI
struct MeasurementUnitView: View {
#State var selectedIndex = unitTypes.firstIndex(of: UserDefaults.standard.string(forKey: "Unit")!)!
var userSettings: UserSettings
var body: some View {
VStack {
Spacer(minLength: 15)
Form {
Section {
Picker(selection: self.$selectedIndex, label: Text("Current UnitType")) {
ForEach(0..<unitTypes.count, id: \.self) {
Text(unitTypes[$0])
}
}.onReceive([self.selectedIndex].publisher.first()) { (value) in
self.savePick()
}
.navigationBarTitle("Change Unit Type", displayMode: .inline)
}
}
}
}
func savePick() {
if (userSettings.unit != unitTypes[selectedIndex]) {
userSettings.unit = unitTypes[selectedIndex]
}
}
}
I use a segmented picker and had a similar requirement. After trying a few things I just used an object that had both an ObservableObjectPublisher and a PassthroughSubject publisher as the selection. That let me satisfy SwiftUI and with an onReceive() I could do other stuff as well.
// Selector for the base and radix
Picker("Radix", selection: $base.value) {
Text("Dec").tag(10)
Text("Hex").tag(16)
Text("Oct").tag(8)
}
.pickerStyle(SegmentedPickerStyle())
// receiver for changes in base
.onReceive(base.publisher, perform: { self.setRadices(base: $0) })
base has both an objectWillChange and a PassthroughSubject<Int, Never> publisher imaginatively called publisher.
class Observable<T>: ObservableObject, Identifiable {
let id = UUID()
let objectWillChange = ObservableObjectPublisher()
let publisher = PassthroughSubject<T, Never>()
var value: T {
willSet { objectWillChange.send() }
didSet { publisher.send(value) }
}
init(_ initValue: T) { self.value = initValue }
}
typealias ObservableInt = Observable<Int>
Defining objectWillChange isn't strictly necessary but when I wrote that I liked to remind myself that it was there.
For people that have to support both iOS 13 and 14, I added an extension which works for both. Don't forget to import Combine.
Extension View {
#ViewBuilder func onChangeBackwardsCompatible<T: Equatable>(of value: T, perform completion: #escaping (T) -> Void) -> some View {
if #available(iOS 14.0, *) {
self.onChange(of: value, perform: completion)
} else {
self.onReceive([value].publisher.first()) { (value) in
completion(value)
}
}
}
}
Usage:
Picker(selection: $selectedIndex, label: Text("Color")) {
Text("Red").tag(0)
Text("Blue").tag(1)
}.onChangeBackwardsCompatible(of: selectedIndex) { (newIndex) in
print("Do something with \(newIndex)")
}
Important note: If you are changing a published property inside an observed object within your completion block, this solution will cause an infinite loop in iOS 13. However, it is easily fixed by adding a check, something like this:
.onChangeBackwardsCompatible(of: showSheet, perform: { (shouldShowSheet) in
if shouldShowSheet {
self.router.currentSheet = .chosenSheet
showSheet = false
}
})
SwiftUI 1 & 2
Use onReceive and Just:
import Combine
import SwiftUI
struct ContentView: View {
#State private var selection = 0
var body: some View {
Picker("Some Label", selection: $selection) {
ForEach(0 ..< 5, id: \.self) {
Text("Number \($0)")
}
}
.onReceive(Just(selection)) {
print("Selected: \($0)")
}
}
}
iOS 14 and CoreData entities with relationships
I ran into this issue while trying to bind to a CoreData entity and found that the following works:
Picker("Level", selection: $contact.level) {
ForEach(levels) { (level: Level?) in
HStack {
Circle().fill(Color.green)
.frame(width: 8, height: 8)
Text("\(level?.name ?? "Unassigned")")
}
.tag(level)
}
}
.onChange(of: contact.level) { _ in savecontact() }
Where "contact" is an entity with a relationship to "level".
The Contact class is an #ObservedObject var contact: Contact
saveContact is a do-catch function to try viewContext.save()...
The very important issue : we must pass something to "tag" modifier of Picker item view (inside ForEach) to let it "identify" items and trigger selection change event. And the value we passed will return to Binding variable with "selection" of Picker.
For example :
Picker(selection: $selected, label: Text("")){
ForEach(data){item in //data's item type must conform Identifiable
HStack{
//item view
}
.tag(item.property)
}
}
.onChange(of: selected, perform: { value in
//handle value of selected here (selected = item.property when user change selection)
})