Realm Swift

1234567891011121314151617181920212223242526final class Book: Object, ObjectKeyIdentifiable {
    @Persisted(primaryKey: true) var id: ObjectId
    @Persisted(indexed: true) var title: String
    @Persisted var year: Int
    @Persisted var author: Author?
}

let realm = try await Realm()

try await realm.asyncWrite {
    realm.add(Book(value: ["title": "Dune", "year": 1965]))
}

// Live and lazy — not loaded into memory until accessed.
let recent = realm.objects(Book.self)
    .where { $0.year >= 1990 }
    .sorted(by: \.year, ascending: false)

let token = recent.observe { changes in
    switch changes {
    case .initial(let books): render(books)
    case .update(_, let deletions, let insertions, let modifications):
        applyDiff(deletions, insertions, modifications)
    case .error(let error): report(error)
    }
}

1234567891011121314151617181920// Realm objects are confined to the thread that created them.
// Passing one across threads throws — use a ThreadSafeReference.
let reference = ThreadSafeReference(to: book)
DispatchQueue.global().async {
    let realm = try! Realm()
    guard let book = realm.resolve(reference) else { return }
    try! realm.write { book.year = 1966 }
}

let config = Realm.Configuration(
    schemaVersion: 2,
    migrationBlock: { migration, oldVersion in
        if oldVersion < 2 {
            migration.enumerateObjects(ofType: Book.className()) { old, new in
                new?["isbn"] = old?["legacyIsbn"] ?? ""
            }
        }
    }
)
Realm.Configuration.defaultConfiguration = config