SwiftUIとRealm

/// An individual item. Part of a `Group`.
final class Item: Object, ObjectKeyIdentifiable {
    /// The unique ID of the Item. `primaryKey: true` declares the
    /// _id member as the primary key to the realm.
    @Persisted(primaryKey: true) var _id: ObjectId
    /// The name of the Item, By default, a random name is generated.
    @Persisted var name = "\(randomAdjectives.randomElement()!) \(randomNouns.randomElement()!)"
    /// A flag indicating whether the user "favorited" the item.
    @Persisted var isFavorite = false
    /// The backlink to the `Group` this item is a part of.
    @Persisted(originProperty: "items") var group: LinkingObjects<Group>
}

/// Represents a collection of items.
final class Group: Object, ObjectKeyIdentifiable {
    /// The unique ID of the Group. `primaryKey: true` declares the
    /// _id member as the primary key to the realm.
    @Persisted(primaryKey: true) var _id: ObjectId
    /// The collection of Items in this group.
    @Persisted var items = RealmSwift.List<Item>()
}

@main
struct ContentView: SwiftUI.App {
    var body: some Scene {
        WindowGroup {
            LocalOnlyContentView()
        }
    }
}

struct LocalOnlyContentView: View {
    // Implicitly use the default realm's objects(Group.self)
    @ObservedResults(Group.self) var groups
    
    var body: some View {
        if let group = groups.first {
            // Pass the Group objects to a view further
            // down the hierarchy
            ItemsView(group: group)
        } else {
            // For this small app, we only want one group in the realm.
            // You can expand this app to support multiple groups.
            // For now, if there is no group, add one here.
            ProgressView().onAppear {
                $groups.append(Group())
            }
        }
    }
}

struct ItemsView: View {
    /// The group is a container for a list of items. Using a group instead of all items
    /// directly allows us to maintain a list order that can be updated in the UI.
    @ObservedRealmObject var group: Group
    /// 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(group.items) { item in
                        ItemRow(item: item)
                    }.onDelete(perform: $group.items.remove)
                    .onMove(perform: $group.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.
                        $group.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()
    }
}