Navigation Bar Items with #EnvironmentObject - ios

Question

I would like to create a Settings view using SwiftUI. I mainly took the official example from Apple about SwiftUI to realize my code. The settings view should have a toggle to whether display or not my favorites items.
For now I have a landmarks list and a settings view.
struct Landmark: Hashable, Codable, Identifiable {
var id: Int
var imageName: String
var title: String
var isFavorite: Bool
var description: String
enum CodingKeys: String, CodingKey {
case id, imageName, title, description
}
}
final class UserData: ObservableObject {
#Published var showFavoriteOnly: Bool = false
#Published var items: [Landmark] = landmarkData
#Published var showProfile: Bool = false
}
struct ItemList: View {
#EnvironmentObject var userData: UserData
#State var trailing: Bool = false
init() {
UITableView.appearance().separatorStyle = .none
}
var body: some View {
NavigationView {
List {
VStack {
CircleBadgeView(text: String(landmarkData.count), thickness: 2)
Text("Tutorials available")
}.frame(minWidth:0, maxWidth: .infinity)
ForEach(userData.items) { landmark in
if !self.userData.showFavoriteOnly || landmark.isFavorite {
ZStack {
Image(landmark.imageName)
.resizable()
.frame(minWidth: 0, maxWidth: .infinity)
.cornerRadius(10)
.overlay(ImageOverlay(text: landmark.title), alignment: .bottomTrailing)
Text(String(landmark.isFavorite))
NavigationLink(destination: TutorialDetailView(landmark: landmark)) {
EmptyView()
}.buttonStyle(PlainButtonStyle())
}
}
}
}.navigationBarTitle("Tutorials")
.navigationBarItems(trailing: trailingItem())
}
}
}
extension ItemList {
func trailingItem () -> some View {
return HStack {
if userData.showProfile {
NavigationLink(destination: ProfileView()) {
Image(systemName: "person.circle")
.imageScale(.large)
.accessibility(label: Text("Profile"))
}
}
NavigationLink(destination: SettingsView().environmentObject(userData)) {
Image(systemName: "gear")
.imageScale(.large)
.accessibility(label: Text("Settings"))
}
}
}
}
As you can see my SettingsView is accessible from navigationBarItems of my NavigationView. I don't know if it's the problem or not but when I put the Toggle inside the ListView it works as expected. But now when I trigger the toggle to enable only favorite my application crash instantly.
I've tried to trigger the Show profile toggle from SettingsView and it works.
struct SettingsView: View {
#EnvironmentObject var userData: UserData
var body: some View {
Form {
Section(header: Text("General")) {
Toggle(isOn: $userData.showProfile) {
Text("Show profile")
}
Toggle(isOn: $userData.showFavoriteOnly) {
Text("Favorites only")
}
}
Section(header: Text("UI")) {
Toggle(isOn: .constant(false)) {
Text("Dark mode")
}
NavigationLink(destination: Text("third")) {
Text("Third navigation")
}
}
}.navigationBarTitle(Text("Settings"), displayMode: .inline)
}
}
In brief, the crash appears in my SettingsView when I trigger the Show only favorite Toggle and then I try to go back to the previous view which is ItemListView
The only information I can get about the error is Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
You can find the whole project on my GitHub : https://github.com/Hurobaki/swiftui-tutorial
Some help would be really appreciated :)

Answer 1

Here is a minimal version of your example code, that works:
struct Landmark: Hashable, Codable, Identifiable {
var id: Int
var imageName: String
var title: String
var isFavorite: Bool
var description: String
}
final class UserData: ObservableObject {
#Published var showFavoriteOnly: Bool = false
#Published var items: [Landmark] = [
Landmark(id: 1, imageName: "a", title: "a", isFavorite: true, description: "A"),
Landmark(id: 2, imageName: "b", title: "b", isFavorite: false, description: "B")
]
}
struct ContentView: View {
#EnvironmentObject var userData: UserData
var body: some View {
NavigationView {
List(userData.items.filter { !userData.showFavoriteOnly || $0.isFavorite }) { landmark in
Text(String(landmark.isFavorite))
}
.navigationBarTitle("Tutorials")
.navigationBarItems(trailing: trailingItem())
}
}
func trailingItem () -> some View {
return HStack {
NavigationLink(destination: SettingsView()) {
Text("Settings")
}
}
}
}
struct SettingsView: View {
#EnvironmentObject var userData: UserData
var body: some View {
Form {
Section(header: Text("General")) {
Toggle(isOn: $userData.showFavoriteOnly) {
Text("Favorites only")
}
}
}.navigationBarTitle(Text("Settings"), displayMode: .inline)
}
}