Make List items selectable in edit mode, EditMode example from documentation not working - swiftui

I want to add the possibility to select items in a list when edit mode is selected, additionally to the delete and move option. Ideally I want to use the existing edit, delete and move buttons instead of writing my own. I tried the example from the documentation. It's not working for me. The value of editMode is always .inactive. I'm using XCode 14. The deployment target of my app is iOS 16.0.
This is my source code:
import SwiftUI
struct ContentView: View {
#Environment(\.editMode)
private var editMode
#State
private var name = "Maria Ruiz"
var body: some View {
NavigationView {
Form {
if editMode?.wrappedValue.isEditing == true {
TextField("Name", text: $name)
} else {
Text("test")
}
}
.animation(nil, value: editMode?.wrappedValue)
.toolbar { // Assumes embedding this view in a NavigationView.
EditButton()
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView().environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
}
}
It always shows the test text. I also tried a variant with the .onChange modifier, with the same result.

Forwarding the fix from https://developer.apple.com/forums/thread/716434:
Try extracting the parts that access the editMode property from the
container that changes based on it, like List/Form.
struct ContentView: View {
var body: some View {
NavigationView {
Form {
MyForm()
}
.toolbar { // Assumes embedding this view in a NavigationView.
EditButton()
}
}
}
}
and
struct MyForm: View {
#Environment(\.editMode)
private var editMode
#State
private var name = "Maria Ruiz"
var body: some View {
Text(String(editMode!.wrappedValue.isEditing))
if editMode?.wrappedValue.isEditing == true {
TextField("Name", text: $name)
} else {
Text("test")
}
}
}

Related

navigate with NavigationStack swiftUI

I am new to SwiftUI framework I am trying to implement NavigationStack. I want to navigate on button action instead of using NavigationLink. The reason behind that is, I need to navigate once a particular function get performed on button action.
struct AView: View {
#State private var actionss = [Int]()
var body: some View {
NavigationStack(path:$actionss) {
VStack{
Button("test") {
actionss.append(0)
}
}
.navigationDestination(for: Int.self) { data in
BView()
}
}
}
}
Above code of "AView" is working fine to navigate "BView". The only thing is I am not able to navigate on "CView" from "BView" without using NavigationLink.
I need to perform particular function before navigate from "BView" to "CView" as well.
Please help me in this.
Thank you in advance.
Assuming that the work is done on BView you can use .navigationDestination as well:
struct AView: View {
#State private var actionss = [Int]()
var body: some View {
NavigationStack(path:$actionss) {
VStack{
Button("show BView") {
actionss.append(0)
}
}
.navigationDestination(for: Int.self) { data in
BView()
}
.navigationTitle("AView")
}
}
}
struct BView: View {
#State var show: Bool = false
var body: some View {
VStack {
Button("show CView") {
show = true
}
}
.navigationDestination(isPresented: $show) {
CView()
}
.navigationTitle("BView")
}
}
struct CView: View {
var body: some View {
Text("Hello")
.navigationTitle("CView")
}
}

SwiftUI publishing an environment change from within view update

The app has a model that stores the user's current preference for light/dark mode, which the user can change by clicking on a button:
class DataModel: ObservableObject {
#Published var mode: ColorScheme = .light
The ContentView's body tracks the model, and adjusts the colorScheme when the model changes:
struct ContentView: View {
#StateObject private var dataModel = DataModel()
var body: some View {
NavigationStack(path: $path) { ...
}
.environmentObject(dataModel)
.environment(\.colorScheme, dataModel.mode)
As of Xcode Version 14.0 beta 5, this is producing a purple warning: Publishing changes from within view updates is not allowed, this will cause undefined behavior. Is there another way to do this? Or is it a hiccup in the beta release? Thanks!
Update: 2022-09-28
Xcode 14.1 Beta 3 (finally) fixed the "Publishing changes from within view updates is not allowed, this will cause undefined behavior"
See: https://www.donnywals.com/xcode-14-publishing-changes-from-within-view-updates-is-not-allowed-this-will-cause-undefined-behavior/
Full disclosure - I'm not entirely sure why this is happening but these have been the two solutions I have found that seem to work.
Example Code
// -- main view
#main
struct MyApp: App {
#StateObject private var vm = ViewModel()
var body: some Scene {
WindowGroup {
ViewOne()
.environmentObject(vm)
}
}
}
// -- initial view
struct ViewOne: View {
#EnvironmentObject private var vm: ViewModel
var body: some View {
Button {
vm.isPresented.toggle()
} label: {
Text("Open sheet")
}
.sheet(isPresented: $vm.isPresented) {
SheetView()
}
}
}
// -- sheet view
struct SheetView: View {
#EnvironmentObject private var vm: ViewModel
var body: some View {
Button {
vm.isPresented.toggle()
} label: {
Text("Close sheet")
}
}
}
// -- view model
class ViewModel: ObservableObject {
#Published var isPresented: Bool = false
}
Solution 1
Note: from my testing and the example below I still get the error to appear. But if I have a more complex/nested app then the error disappears..
Adding a .buttonStyle() to the button that does the initial toggling.
So within the ContentView on the Button() {} add in a .buttonStyle(.plain) and it will remove the purple error:
struct ViewOne: View {
#EnvironmentObject private var vm: ViewModel
var body: some View {
Button {
vm.isPresented.toggle()
} label: {
Text("Open sheet")
}
.buttonStyle(.plain) // <-- here
.sheet(isPresented: $vm.isPresented) {
SheetView()
}
}
}
^ This is probably more of a hack than solution since it'll output a new view from the modifier and that is probably what is causing it to not output the error on larger views.
Solution 2
This one is credit to Alex Nagy (aka. Rebeloper)
As Alex explains:
.. with SwiftUI 3 and SwiftUI 4 the data handling kind of changed. How SwiftUI handles, more specifically the #Published variable ..
So the solution is to have the boolean trigger to be a #State variable within the view and not as a #Published one inside the ViewModel. But as Alex points out it can make your views messy and if you have a lot of states in it, or not be able to deep link, etc.
However, since this is the way that SwiftUI 4 wants these to operate, we run the code as such:
// -- main view
#main
struct MyApp: App {
var body: some Scene {
WindowGroup {
ViewOne()
}
}
}
// -- initial view
struct ViewOne: View {
#State private var isPresented = false
var body: some View {
Button {
isPresented.toggle()
} label: {
Text("Open sheet")
}
.sheet(isPresented: $isPresented) {
SheetView(isPresented: $isPresented)
// SheetView() <-- if using dismiss() in >= iOS 15
}
}
}
// -- sheet view
struct SheetView: View {
// I'm showing a #Binding here for < iOS 15
// but you can use the dismiss() option if you
// target higher
// #Environment(\.dismiss) private var dismiss
#Binding var isPresented: Bool
var body: some View {
Button {
isPresented.toggle()
// dismiss()
} label: {
Text("Close sheet")
}
}
}
Using the #Published and the #State
Continuing from the video, if you need to still use the #Published variable as it might tie into other areas of your app you can do so with a .onChange and a .onReceive to link the two variables:
struct ViewOne: View {
#EnvironmentObject private var vm: ViewModel
#State private var isPresented = false
var body: some View {
Button {
vm.isPresented.toggle()
} label: {
Text("Open sheet")
}
.sheet(isPresented: $isPresented) {
SheetView(isPresented: $isPresented)
}
.onReceive(vm.$isPresented) { newValue in
isPresented = newValue
}
.onChange(of: isPresented) { newValue in
vm.isPresented = newValue
}
}
}
However, this can become really messy in your code if you have to trigger it for every sheet or fullScreenCover.
Creating a ViewModifier
So to make it easier for you to implement it you can create a ViewModifier which Alex has shown works too:
extension View {
func sync(_ published: Binding<Bool>, with binding: Binding<Bool>) -> some View {
self
.onChange(of: published.wrappedValue) { newValue in
binding.wrappedValue = newValue
}
.onChange(of: binding.wrappedValue) { newValue in
published.wrappedValue = newValue
}
}
}
And in use on the View:
struct ViewOne: View {
#EnvironmentObject private var vm: ViewModel
#State private var isPresented = false
var body: some View {
Button {
vm.isPresented.toggle()
} label: {
Text("Open sheet")
}
.sheet(isPresented: $isPresented) {
SheetView(isPresented: $isPresented)
}
.sync($vm.isPresented, with: $isPresented)
// .onReceive(vm.$isPresented) { newValue in
// isPresented = newValue
// }
// .onChange(of: isPresented) { newValue in
// vm.isPresented = newValue
// }
}
}
^ Anything denoted with this is my assumptions and not real technical understanding - I am not a technical knowledgeable :/
Try running the code that's throwing the purple error asynchronously, for example, by using DispatchQueue.main.async or Task.
DispatchQueue.main.async {
// environment changing code comes here
}
Task {
// environment changing code comes here
}
Improved Solution of Rebel Developer
as a generic function.
Rebeloper solution
It helped me a lot.
1- Create extension for it:
extension View{
func sync<T:Equatable>(_ published:Binding<T>, with binding:Binding<T>)-> some View{
self
.onChange(of: published.wrappedValue) { published in
binding.wrappedValue = published
}
.onChange(of: binding.wrappedValue) { binding in
published.wrappedValue = binding
}
}
}
2- sync() ViewModel #Published var to local #State var
struct ContentView: View {
#EnvironmentObject var viewModel:ViewModel
#State var fullScreenType:FullScreenType?
var body: some View {
//..
}
.sync($viewModel.fullScreenType, with: $fullScreenType)

SwiftUI - TabView/NavigationLink navigation breaks when using a custom binding

I'm having trouble with what I think may be a bug, but most likely me doing something wrong.
I have a slightly complex navigation state variable in my model that I'm using for tracking/setting state between tab and sidebar presentations when multitasking on iPad. That all works fine except in tab mode, once I use a navigation link once I can't seem to use one again, whether the binding is on my tab view or navigation links in a list.
Would really appreciate any thoughts on this,
Cheers!
Example
NavigationItem.swift
enum SubNavigationItem: Hashable {
case overview, user, hobby
}
enum NavigationItem: Hashable {
case home(SubNavigationItem)
case settings
}
Model.swift
final class Model: ObservableObject {
#Published var selectedTab: NavigationItem = .home(.overview)
}
SwiftUIApp.swift
#main
struct SwiftUIApp: App {
#StateObject var model = Model()
var body: some Scene {
WindowGroup {
ContentView()
.environmentObject(model)
}
}
}
ContentView.swift
struct ContentView: View {
var body: some View {
AppTabNavigation()
}
}
AppTabNavigation.swift
struct AppTabNavigation: View {
#EnvironmentObject private var model: Model
var body: some View {
TabView(selection: $model.selectedTab) {
NavigationView {
HomeView()
}
.tabItem {
Label("Home", systemImage: "house")
}
.tag(NavigationItem.home(.overview))
NavigationView {
Text("Settings View")
}
.tabItem {
Label("Settings", systemImage: "gear")
}
.tag(NavigationItem.settings)
}
}
}
HomeView.swift
I created a binding here because selection required an optional <NavigationItem?> not
struct HomeView: View {
#EnvironmentObject private var model: Model
var body: some View {
let binding = Binding<NavigationItem?>(
get: {
model.selectedTab
},
set: {
guard let item = $0 else { return }
model.selectedTab = item
}
)
List {
NavigationLink(
destination: Text("Users"),
tag: .home(.user),
selection: binding
) {
Text("Users")
}
NavigationLink(
destination: Text("Hobbies"),
tag: .home(.hobby),
selection: binding
) {
Text("Hobbies")
}
}
.navigationTitle("Home")
}
}
Second Attempt
I tried making the selectedTab property optional as #Lorem Ipsum suggested. Which means I can remove the binding there. But then the TabView doesn't work with the property. So I create a binding for that and have the same issue but with the tab bar!
Make the selected tab optional
#Published var selectedTab: NavigationItem? = .home(.overview)
And get rid of that makeshift binding variable. Just use the variable
$model.selectedTab
If the variable can never be nil then something is always selected IAW with that makeshift variable it will just keep the last value.

SwiftUI #EnvironmentObejct can't seem update values

I'm trying to use #EnvironmentObject to update the Boolean values in the ViewModel. So when I navigate back to the original screen I want the boolean values to have change and therefore changing the text. Tried this with ObservedObject too. This is not working or can not find a way for ContentView to redraw itself upon change.
import SwiftUI
class Global: ObservableObject {
#Published var change = [false, false]
}
struct ContentView: View {
var body: some View {
NavigationView {
VStack {
NewView().environmentObject(Global())
}
}
}
}
struct NewView: View {
#EnvironmentObject var env: Global
var body: some View {
Text(env.change[1] ? "WORKS" : "DOESNT WORK")
NavigationLink(destination: ChangeThis().environmentObject(Global())) {
Text("Push Me to Change")
}
}
}
struct ChangeThis: View {
#EnvironmentObject var env: Global
var body: some View {
Button(action: {
env.change[0] = true
env.change[1] = true
}) {
Text(" Want this to Changes the Boolean values in Global and update NewView with those values after clicking back")
}
}
}
You need to use the same instance of the Global EnvironmentObject in all your views:
struct NewView: View {
#EnvironmentObject var env: Global
...
// pass the already-existing instance, don't create a new one
NavigationLink(destination: ChangeThis().environmentObject(env)
...
}

How to disable NavigationView push and pop animations

Given this simple NavigationView:
struct ContentView : View {
var body: some View {
NavigationView {
VStack {
NavigationLink("Push Me", destination: Text("PUSHED VIEW"))
}
}
}
}
Did anyone find a way of disabling the NavigationView animation when a destination view is pushed/popped into/from the stack?
This has been possible in UIKit since iOS2.0! I think it is not too much to ask from the framework. I tried all sorts of modifiers on all views (i.e., the NavigationView container, the destination view, the NavigationLink, etc)
These are some of the modifiers I tried:
.animation(nil)
.transition(.identity)
.transaction { t in t.disablesAnimations = true }
.transaction { t in t.animation = nil }
None made a difference. I did not find anything useful in the EnvironmentValues either :-(
Am I missing something very obvious, or is the functionality just not there yet?
Xcode 11.3:
Right now there is no modifier to disable NavigationView animations.
You can use your struct init() to disable animations, as below:
struct ContentView : View {
init(){
UINavigationBar.setAnimationsEnabled(false)
}
var body: some View {
NavigationView {
VStack {
NavigationLink("Push Me", destination: Text("PUSHED VIEW"))
}
}
}
}
First you need state for the NavigationLink to respond to, then set that state inside a transaction with animations disabled, as follows:
struct ContentView : View {
#State var isActive = false
var body: some View {
NavigationView {
VStack {
NavigationLink(isActive: $isActive, destination: {
Text("PUSHED VIEW")}) {
Text("Push Me")
}
Button("Navigate Without Animation") {
var transaction = Transaction()
transaction.disablesAnimations = true
withTransaction(transaction) {
isActive = true
}
}
}
}
}
}
I recently created an open source project called swiftui-navigation-stack (https://github.com/biobeats/swiftui-navigation-stack) that contains the NavigationStackView, a view that mimics the navigation behaviours of the standard NavigationView adding some useful features. For example, you could use the NavigationStackView and disable the transition animations as requested by Kontiki in the question. When you create the NavigationStackView just specify .none as transitionType:
struct ContentView : View {
var body: some View {
NavigationStackView(transitionType: .none) {
ZStack {
Color.yellow.edgesIgnoringSafeArea(.all)
PushView(destination: View2()) {
Text("PUSH")
}
}
}
}
}
struct View2: View {
var body: some View {
ZStack {
Color.green.edgesIgnoringSafeArea(.all)
PopView {
Text("POP")
}
}
}
}
PushView and PopView are two views that allow you push and pop views (similar to the SwiftUI NavigationLink). Here is the complete example:
import SwiftUI
import NavigationStack
struct ContentView : View {
var body: some View {
NavigationStackView(transitionType: .none) {
ZStack {
Color.yellow.edgesIgnoringSafeArea(.all)
PushView(destination: View2()) {
Text("PUSH")
}
}
}
}
}
struct View2: View {
var body: some View {
ZStack {
Color.green.edgesIgnoringSafeArea(.all)
PopView {
Text("POP")
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
The result is:
It would be great if you guys joined me in improving this open source project.