SwiftUI QuickStart와 함께 Realm 사용

import RealmSwift
import SwiftUI

/// Random adjectives for more interesting demo item names
let randomAdjectives = [
    "fluffy", "classy", "bumpy", "bizarre", "wiggly", "quick", "sudden",
    "acoustic", "smiling", "dispensable", "foreign", "shaky", "purple", "keen",
    "aberrant", "disastrous", "vague", "squealing", "ad hoc", "sweet"
]
/// Random noun for more interesting demo item names
let randomNouns = [
    "floor", "monitor", "hair tie", "puddle", "hair brush", "bread",
    "cinder block", "glass", "ring", "twister", "coasters", "fridge",
    "toe ring", "bracelet", "cabinet", "nail file", "plate", "lace",
    "cork", "mouse pad"
]
/// An individual item. Part of an `ItemGroup`.
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
    /// Users can enter a description, which is an empty string by default
    @Persisted var itemDescription = ""
    
    /// The backlink to the `ItemGroup` this item is a part of.
    @Persisted(originProperty: "items") var group: LinkingObjects<ItemGroup>
    
    /// Store the user.id as the ownerId so you can query for the user's objects with Flexible Sync
    /// Add this to both the `ItemGroup` and the `Item` objects so you can read and write the linked objects.
    @Persisted var ownerId = ""
}
/// Represents a collection of items.
final class ItemGroup: Object, ObjectKeyIdentifiable {
    /// The unique ID of the ItemGroup. `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>()
    
    /// Store the user.id as the ownerId so you can query for the user's objects with Flexible Sync
    /// Add this to both the `ItemGroup` and the `Item` objects so you can read and write the linked objects.
    @Persisted var ownerId = ""
}

/// 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 {
    @State var searchFilter: String = ""
    // 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 an ItemGroup. Implements functionality for adding, rearranging,
/// and deleting items in the ItemGroup.
struct ItemsView: View {
    @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
                Task {
                    do {
                        let user = try await app!.login(credentials: .anonymous)
                        // Other views are observing the app and will detect
                        // that the currentUser has changed. Nothing more to do here.
                        print("Logged in as user with id: \(user.id)")
                    } catch {
                        print("Failed to log in: \(error.localizedDescription)")
                        // Set error to observed property so it can be displayed
                        self.error = error
                        return
                    }
                }
            }.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
            Task {
                do {
                    try await app!.currentUser!.logOut()
                    // Other views are observing the app and will detect
                    // that the currentUser has changed. Nothing more to do here.
                } catch {
                    print("Error logging out: \(error.localizedDescription)")
                }
            }
        }.disabled(app!.currentUser == nil || isLoggingOut)
    }
}