Realm Database with SwiftUI QuickStart

import RealmSwift
import SwiftUI

/// The main screen that determines whether to present the SyncContentView or the LocalOnlyContentView.
/// For now, it always displays the LocalOnlyContentView.
@main
struct ContentView: SwiftUI.App {
    var body: some Scene {
        WindowGroup {
            LocalOnlyContentView()
        }
    }
}

/// The main content view if not using Sync.
struct LocalOnlyContentView: View {
    // Implicitly use the default realm's objects(ItemGroup.self)
    @ObservedResults(ItemGroup.self) var itemGroups
    
    var body: some View {
        if let itemGroup = itemGroups.first {
            // Pass the ItemGroup objects to a view further
            // down the hierarchy
            ItemsView(itemGroup: itemGroup)
        } else {
            // For this small app, we only want one itemGroup in the realm.
            // You can expand this app to support multiple itemGroups.
            // For now, if there is no itemGroup, add one here.
            ProgressView().onAppear {
                $itemGroups.append(ItemGroup())
            }
        }
    }
}

/// The screen containing a list of items in a itemGroup. Implements functionality for adding, rearranging,
/// and deleting items in the itemGroup.
struct ItemsView: View {
    /// The itemGroup is a container for a list of items. Using an itemGroup instead of all items
    /// directly allows us to maintain a list order that can be updated in the UI.
    @ObservedRealmObject var itemGroup: ItemGroup
    /// The button to be displayed on the top left.
    var leadingBarButton: AnyView?
    var body: some View {
        NavigationView {
            VStack {
                // The list shows the items in the realm.
                List {
                    ForEach(itemGroup.items) { item in
                        ItemRow(item: item)
                    }.onDelete(perform: $itemGroup.items.remove)
                    .onMove(perform: $itemGroup.items.move)
                }.listStyle(GroupedListStyle())
                    .navigationBarTitle("Items", displayMode: .large)
                    .navigationBarBackButtonHidden(true)
                    .navigationBarItems(
                        leading: self.leadingBarButton,
                        // Edit button on the right to enable rearranging items
                        trailing: EditButton())
                // Action bar at bottom contains Add button.
                HStack {
                    Spacer()
                    Button(action: {
                        // The bound collection automatically
                        // handles write transactions, so we can
                        // append directly to it.
                        $itemGroup.items.append(Item())
                    }) { Image(systemName: "plus") }
                }.padding()
            }
        }
    }
}

/// Represents an Item in a list.
struct ItemRow: View {
    @ObservedRealmObject var item: Item
    var body: some View {
        // You can click an item in the list to navigate to an edit details screen.
        NavigationLink(destination: ItemDetailsView(item: item)) {
            Text(item.name)
            if item.isFavorite {
                // If the user "favorited" the item, display a heart icon
                Image(systemName: "heart.fill")
            }
        }
    }
}
/// Represents a screen where you can edit the item's name.
struct ItemDetailsView: View {
    @ObservedRealmObject var item: Item
    var body: some View {
        VStack(alignment: .leading) {
            Text("Enter a new name:")
            // Accept a new name
            TextField("New name", text: $item.name)
                .navigationBarTitle(item.name)
                .navigationBarItems(trailing: Toggle(isOn: $item.isFavorite) {
                    Image(systemName: item.isFavorite ? "heart.fill" : "heart")
                })
        }.padding()
    }
}

/// Represents the login screen. We will have a button to log in anonymously.
struct LoginView: View {
    // Hold an error if one occurs so we can display it.
    @State var error: Error?
    
    // Keep track of whether login is in progress.
    @State var isLoggingIn = false
    var body: some View {
        VStack {
            if isLoggingIn {
                ProgressView()
            }
            if let error = error {
                Text("Error: \(error.localizedDescription)")
            }
            Button("Log in anonymously") {
                // Button pressed, so log in
                isLoggingIn = true
                app!.login(credentials: .anonymous) { result in
                    isLoggingIn = false
                    if case let .failure(error) = result {
                        print("Failed to log in: \(error.localizedDescription)")
                        // Set error to observed property so it can be displayed
                        self.error = error
                        return
                    }
                    // Other views are observing the app and will detect
                    // that the currentUser has changed. Nothing more to do here.
                    print("Logged in")
                }
            }.disabled(isLoggingIn)
        }
    }
}

/// A button that handles logout requests.
struct LogoutButton: View {
    @State var isLoggingOut = false
    var body: some View {
        Button("Log Out") {
            guard let user = app!.currentUser else {
                return
            }
            isLoggingOut = true
            user.logOut() { error in
                isLoggingOut = false
                // Other views are observing the app and will detect
                // that the currentUser has changed. Nothing more to do here.
                print("Logged out")
            }
        }.disabled(app!.currentUser == nil || isLoggingOut)
    }
}