Show a .sheet with a bool from Core Data - swiftui

I have a sheet which displays a guide for my app.
the sheet isPresented by a local bool showingGuide.
I want that local bool to mirror a bool in Core Data in my settings entity with the bool showGuide
I know how to save and retrieve the state of the bool in general but retrieving the bool in core data on app launch is where i'm getting stuck.
When the user hits the button 'Got it!' I'm wanting the guide to never show again. (Maybe i might setup a button in the settings view that can activate it again if they need a refresher)
I've tried playing with a custom initialiser of the Test view that tries to retrieve settings.showGuide but have had no luck.
I also understand that settings is an array so i'll have to always save and retrieve into first item in the settings array. Is there an easier way to do that? save one entity instead of an array?
Any ideas?
import Foundation
import SwiftUI
import CoreData
struct Test: View {
#Environment(\.managedObjectContext) var managedObjectContext
#FetchRequest(fetchRequest: Settings.getSettings()) var settings:FetchedResults<Settings>
#State private var showingGuide = true
var body: some View{
VStack{
Text("Hello")
}
.sheet(isPresented: $showingGuide) {
MainGuide().padding(.horizontal)
Button(action: {
let settings = Settings(context: self.managedObjectContext)
settings.showGuide = false
self.showingGuide = false
do {
try self.managedObjectContext.save()
}catch{
print(error)
}
}){
Text("Got it!")
}.padding()
}
}
}

Your are not supposed to set a #State-variable programatically (link). Instead, use an if-statement that depends on the boolean from your CoreData-object to display the sheet or not.
I also recommend to add a computed variable for the settings object as it is always the first element in the array as shown in the code below for var settings.
You can do it like this:
struct ContentView: View {
#Environment(\.managedObjectContext) var managedObjectContext
#FetchRequest(
entity: Settings.entity(),
sortDescriptors: [
NSSortDescriptor(keyPath: \Settings.self, ascending: false)
]
) var settingsRequest: FetchedResults<Settings>
var settings:Settings{
settingsRequest[0]
}
#State var showGuide:Bool = true
var body: some View{
VStack{
if settings.showSheet{
Text("show sheet: \(String(settings.showSheet))").sheet(isPresented: $showGuide){
Text("Hello from Sheet")
Button(action: {
self.settings.showSheet = false
self.showGuide = false
do {
try self.managedObjectContext.save()
}catch{
print(error)
}
}){
Text("Got it!")
}.padding()
}
}else{
Text("already agreed")
}
}
}
}
Note: This will only set settings.showSheet to true if the user click on the button. When dismissing the sheet by swiping, it will not update CoreData. If you want to perform some action on the swiping action, you could use .onDismiss(perform: { }).

Related

Is it possible to reload only modified item in SwiftUI List/ForEach that uses #Binding

Simple sample code with toggle button (slightly modified from hackingwithswift:
This code(hackingwithswift original and my version) IS redrawing every list cell whenever any toggle happens. I modified code to better debug view drawing.
import SwiftUI
struct User: Identifiable {
let id = UUID()
var name: String
var isContacted = false
}
struct ProfileView: View {
#State private var users = [
User(name: "Taylor"),
User(name: "Justin"),
User(name: "Adele")
]
var body: some View {
let _ = Self._printChanges()
List($users) { $user in
ProfileCell(user: $user)
}
}
}
struct ProfileCell: View{
#Binding var user: User
var body: some View{
let _ = Self._printChanges()
Text(user.name)
Spacer()
Toggle("User has been contacted", isOn: $user.isContacted)
.labelsHidden()
}
}
Running app and toggling will print following in console for every toggle:
ProfileView: _users changed.
ProfileCell: #self, _user changed.
ProfileCell: #self, _user changed.
ProfileCell: #self, _user changed.
Hackingwithswift tutorial states "Using a binding in this way is the most efficient way of modifying the list, because it won’t cause the entire view to reload when only a single item changes.", however that does not seem to be true.
Is it possible to redraw only item that was changed?
Theoretically it should be working, but it seems they changed something since first introduction, because now on state change they recreate(!) bindings (all of them), so automatic view changes handler interpret that as view update (binding is a property after all).
A possible workaround for this is to help rendering engine and check view equitability manually.
Tested with Xcode 13.4 / iOS 15.5
Main parts:
// 1
List($users) { $user in
EquatableView(content: ProfileCell(user: $user)) // << here !!
}
// 2
struct ProfileCell: View, Equatable {
static func == (lhs: ProfileCell, rhs: ProfileCell) -> Bool {
lhs.user == rhs.user
}
// ...
// 3
struct User: Identifiable, Equatable {
Test module is here

Sheet is Only Presented Once in SwiftUI

I have an app which presents a sheet. It works for the first time but when I click on it again it does not work. I am making isPresented false when you dismiss a sheet but when I tap on the Filter button again, it does not show the sheet.
ContentView
struct ContentView: View {
#State private var isPresented: Bool = false
var body: some View {
NavigationView {
List(1...20, id: \.self) { index in
Text("\(index)")
}.listStyle(.plain)
.navigationTitle("Hotels")
.toolbar {
Button("Filters") {
isPresented = true
}
}
.sheet(isPresented: $isPresented) {
isPresented = false
} content: {
FilterView()
}
}
}
}
FilterView:
import SwiftUI
struct FilterView: View {
#Environment(\.presentationMode) private var presentationMode
var body: some View {
ZStack {
Text("FilterView")
Button {
// action
presentationMode.wrappedValue.dismiss()
} label: {
Text("Dismiss")
}
}
}
}
struct FilterView_Previews: PreviewProvider {
static var previews: some View {
FilterView()
}
}
A couple of things to note from my experience.
Firstly, when using the isPresented binding to show a sheet, you don't need to reset the bound value in a custom onDismiss handler to reset it to false - that's handled for you internally by SwiftUI as part of the dismiss action.
So your modifier can be simplified a little:
.sheet(isPresented: $isPresented) {
FilterView()
}
Secondly, when running an app in the Simulator I've noticed that when you come back to the main view after dismissing a sheet you have to interact with the app somehow before clicking on the toolbar button, or the action won't trigger.
In cases like this, just scrolling the list up or down a little would be enough, and then the toolbar button works as you'd expect.
I've not encountered the same thing while running apps on a physical device – whether that's because the bug isn't present, or just that it's a lot easier to interact with the app in some microscopic form of gesture, I couldn't say.

SwiftUI #State variables aren't updated

I basically have the same code as in this question. The problem I have is that when the tapGesture event happens, the sheet shows (the sheet code is called) but debug shows that showUserEditor is false (in that case, how is the sheet showing...?) and that selectedUserId is still nil (and therefore crashes on unwrapping it...)
The view:
struct UsersView: View {
#Environment(\.managedObjectContext)
private var viewContext
#FetchRequest(
sortDescriptors: [NSSortDescriptor(keyPath: \User.nickname, ascending: true)],
animation: .default)
private var users: FetchedResults<User>
#State private var selectedUserId : NSManagedObjectID? = nil
#State private var showUserEditor = false
var body: some View {
NavigationView {
List {
ForEach(users) { user in
UserRowView(user: user)
.onTapGesture {
self.selectedUserId = user.objectID
self.showUserEditor = true
}
}
}
}.sheet(isPresented: $showUserEditor) {
UserEditorView(userId: self.selectedUserId!)
}
}
}
If you want, I can publish the editor and the row but they seem irrelevant to the question as the magic should happen in the view.
So, I still haven't figured out WHY the code posted in the question didn't work, with a pointer from #loremipsum I got a working code by using another .sheet() method, one that takes an optional Item and not a boolean flag. The code now looks like this and works, but still if anyone can explain why the posted code didn't work I'd appreciate it.
struct UsersView: View {
#Environment(\.managedObjectContext)
private var viewContext
#FetchRequest(
sortDescriptors: [NSSortDescriptor(keyPath: \User.nickname, ascending: true)],
animation: .default)
private var users: FetchedResults<User>
#State private var selectedUser : User? = nil
var body: some View {
NavigationView {
List {
ForEach(users) { user in
UserRowView(user: user)
.onTapGesture {
self.selectedUser = user
}
}.onDelete(perform: deleteItems)
}
}.sheet(item: $selectedUser, onDismiss: nil) { user in
UserEditorView(user: user)
}
}
}
struct == immutable and SwiftUI decides when the struct gets init and reloaded
Working with code that depends on SwiftUI updating non-wrapped variables at a very specific time is not recommended. You have no control over this process.
To make your first setup work you need to use SwiftUI wrappers for the variables
.sheet(isPresented: $showUserEditor) {
//struct == immutable SwiftUI wrappers load the entire struct when there are changes
//With your original setup this variable gets created/set when the body is loaded so the orginal value of nil is what is seen in the next View
UserEditorView1(userId: $selectedUserId)
}
struct UserEditorView1: View {
//This is what you orginal View likely looks like it won't work because of the struct being immutable and SwiftUI controlling when the struct is reloaded
//let userId: NSManagedObjectID? <---- Depends on specific reload steps
//To make it work you would use a SwiftUI wrapper so the variable gets updated when SwiftUI descides to update it which is invisible to the user
#Binding var userId: NSManagedObjectID?
//This setup though now requres you to go fetch the object somehow and put it into the View so you can edit it.
//It is unnecessary though because SwiftUI provides the .sheet init with item where the item that is set gets passed directly vs waiting for the SwiftUi update no optionals
var body: some View {
Text(userId?.description ?? "nil userId")
}
}
Your answer code doesn't work because your parameter is optional and Binding does not like optionals
struct UserEditorView2: View {
//This is the setup that you posted in the Answer code and it doesn't work becaue of the ? Bindings do not like nil. You have to create wrappers to compensate for this
//But unecessary because all CoreData objects are ObservableObjects so you dont need Binding here the Binding is built-in the object for editing the variables
#Binding var user: User?
var body: some View {
TextField("nickname", text: $user.nickname)
}
}
Now for working code with an easily editable CoreData Object
struct UsersView: View {
#Environment(\.managedObjectContext)
private var viewContext
#FetchRequest(
sortDescriptors: [NSSortDescriptor(keyPath: \User.nickname, ascending: true)],
animation: .default)
private var users: FetchedResults<User>
//Your list view would use the CoreData object to trigger a sheet when the new value is available. When nil there will not be a sheet available for showing
#State private var selectedUser : User? = nil
var body: some View {
NavigationView {
List {
ForEach(users) { user in
UserRowView(user: user)
.onTapGesture {
self.selectedUser = user
}
}
}
}.sheet(item: $selectedUser, onDismiss: nil) { user in //This gives you a non-optional user so you don't have to compensate for nil in the next View
UserEditorView3(user: user)
}
}
}
Then the View in the sheet would look like this
struct UserEditorView3: View {
//I mentioned the ObservedObject in my comment
#ObservedObject var user: User
var body: some View {
//If your nickname is a String? you have to compensate for that optional but it is much simpler to do it from here
TextField("nickname", text: $user.nickname.bound)
}
}
//This comes from another very popular SO question (couldn't find it to quote it) that I could not find and is necessary when CoreData does not let you define a variable as non-optional and you want to use Binding for editing
extension Optional where Wrapped == String {
var _bound: String? {
get {
return self
}
set {
self = newValue
}
}
public var bound: String {
get {
//This just give you an empty String when the variable is nil
return _bound ?? ""
}
set {
_bound = newValue.isEmpty ? nil : newValue
}
}
}

SwiftUI - How to pass data then initialise and edit data

I'm downloading data from Firebase and trying to edit it. It works, but with an issue. I am currently passing data to my EditViewModel with the .onAppear() method of my view. And reading the data from EditViewModel within my view.
class EditViewModel: ObservableObject {
#Published var title: String = ""
}
struct EditView: View {
#State var selected_item: ItemModel
#StateObject var editViewModel = EditViewModel()
var body: some View {
VStack {
TextField("Name of item", text: self.$editViewModel.title)
Divider()
}.onAppear {
DispatchQueue.main.async {
editViewModel.title = selected_item.title
}
}
}
}
I have given you the extremely short-hand version as it's much easier to follow.
However, I push to another view to select options from a list and pop back. As a result, everything is reset due to using the onAppear method. I have spent hours trying to use init() but I am struggling to get my application to even compile, getting errors in the process. I understand it's due to using the .onAppear method, but how can I use init() for this particular view/view-model?
I've search online but I've found the answers to not be useful, or different from what I wish to achieve.
Thank you.
You don't need to use State for input property - it is only for internal view usage. So as far as I understood your scenario, here is a possible solution:
struct EditView: View {
private var selected_item: ItemModel
#StateObject var editViewModel = EditViewModel()
init(selectedItem: ItemModel) {
selected_item = selectedItem
editViewModel.title = selectedItem.title
}
var body: some View {
VStack {
TextField("Name of item", text: self.$editViewModel.title)
Divider()
}.onAppear {
DispatchQueue.main.async {
editViewModel.title = selected_item.title
}
}
}
}

Disable drag to dismiss in SwiftUI Modal

I've presented a modal view but I would like the user to go through some steps before it can be dismissed.
Currently the view can be dragged to dismiss.
Is there a way to stop this from being possible?
I've watched the WWDC Session videos and they mention it but I can't seem to put my finger on the exact code I'd need.
struct OnboardingView2 : View {
#Binding
var dismissFlag: Bool
var body: some View {
VStack {
Text("Onboarding here! πŸ™ŒπŸΌ")
Button(action: {
self.dismissFlag.toggle()
}) {
Text("Dismiss")
}
}
}
}
I currently have some text and a button I'm going to use at a later date to dismiss the view.
iOS 15+
Starting from iOS 15 we can use interactiveDismissDisabled:
func interactiveDismissDisabled(_ isDisabled: Bool = true) -> some View
We just need to attach it to the sheet. Here is an example from the documentation:
struct PresentingView: View {
#Binding var showTerms: Bool
var body: some View {
AppContents()
.sheet(isPresented: $showTerms) {
Sheet()
}
}
}
struct Sheet: View {
#State private var acceptedTerms = false
var body: some View {
Form {
Button("Accept Terms") {
acceptedTerms = true
}
}
.interactiveDismissDisabled(!acceptedTerms)
}
}
It is easy if you use the 3rd party lib Introspect, which is very useful as it access the corresponding UIKit component easily. In this case, the property in UIViewController:
VStack { ... }
.introspectViewController {
$0.isModalInPresentation = true
}
Not sure this helps or even the method to show the modal you are using but when you present a SwiftUI view from a UIViewController using UIHostingController
let vc = UIHostingController(rootView: <#your swiftUI view#>(<#your parameters #>))
you can set a modalPresentationStyle. You may have to decide which of the styles suits your needs but .currentContext prevents the dragging to dismiss.
Side note:I don't know how to dismiss a view presented from a UIHostingController though which is why I've asked a Q myself on here to find out πŸ˜‚
I had a similar question here
struct Start : View {
let destinationView = SetUp()
.navigationBarItem(title: Text("Set Up View"), titleDisplayMode: .automatic, hidesBackButton: true)
var body: some View {
NavigationView {
NavigationButton(destination: destinationView) {
Text("Set Up")
}
}
}
}
The main thing here is that it is hiding the back button. This turns off the back button and makes it so the user can't swipe back ether.
For the setup portion of your app you could create a new SwiftUI file and add a similar thing to get home, while also incorporating your own setup code.
struct SetUp : View {
let destinationView = Text("Your App Here")
.navigationBarItem(title: Text("Your all set up!"), titleDisplayMode: .automatic, hidesBackButton: true)
var body: some View {
NavigationView {
NavigationButton(destination: destinationView) {
Text("Done")
}
}
}
}
There is an extension to make controlling the modal dismission effortless, at https://gist.github.com/mobilinked/9b6086b3760bcf1e5432932dad0813c0
A temporary solution before the official solution released by Apple.
/// Example:
struct ContentView: View {
#State private var presenting = false
var body: some View {
VStack {
Button {
presenting = true
} label: {
Text("Present")
}
}
.sheet(isPresented: $presenting) {
ModalContent()
.allowAutoDismiss { false }
// or
// .allowAutoDismiss(false)
}
}
}