Create Realm Objects - Kotlin SDK

Create an Object

Instantiate Realm objects as you would any other object. In a transaction, you can add the object to the realm if the realm's schema includes the object type. When you add an instance to the realm, it becomes managed by that realm.

To persist a new object to a realm:

1. Instantiate a new object instance with the class constructor. You can use an apply block to configure multiple properties at once.

2. Open a write transaction with realm.write() or realm.writeBlocking().

3. Pass the new object instance to copyToRealm() to persist the object data to the realm. This method returns a managed instance of the object. You can modify the persisted object through the returned instance.

realm.write {
    this.copyToRealm(Frog().apply {
        name = "Kermit"
        age = 45
        species = "Green"
        owner = "Jim"
    })
}

Create a Collection

You can create collections of items using RealmList, RealmSet, and RealmDictionary types.

You can also register a notification handler to listen for changes to a collection. For more information, see React To Changes.

realm.write {
    // Create a Frog object named 'Kermit'
    // Add item to the RealmSet using the add() method
    val frog = copyToRealm(
        Frog().apply {
            name = "Kermit"
            favoriteSnacks.add(Snack().apply { name = "flies" })
        }
    )
    println(frog.favoriteSnacks.first().name) // prints "flies"
}

realm.write {
    val frog = query<Frog>().find().first()
    val snackSet = frog.favoriteSnacks
    // Create two more Snack objects
    val cricketsSnack = copyToRealm(
        Snack().apply {
            name = "crickets"
        }
    )
    val wormsSnack = copyToRealm(
        Snack().apply {
            name = "worms"
        }
    )
    // Add multiple items to the RealmSet using the addAll() method
    snackSet.addAll(setOf(cricketsSnack, wormsSnack))
}

realm.write {
    this.copyToRealm(Frog().apply {
        name = "Kermit"
        favoritePondsByForest = realmDictionaryOf("Hundred Acre Wood" to "Picnic Pond", "Lothlorien" to "Linya")
    })
}

// Percent encode . or $ characters to use them in map keys
val mapKey = "Hundred Acre Wood.Northeast"
val encodedMapKey = "Hundred Acre Wood%2ENortheast"

Create an Embedded Object

To create an embedded object, assign an instance of the EmbeddedRealmObject to a parent object's property:

// Create a parent object with one embedded address
realm.write {
    val contact = copyToRealm(Contact())
        contact.apply {
            name = "Nick Riviera"
            // Embed the address in the contact object
            address = Address().apply {
                street = "123 Fake St"
                city = "Some Town"
                state = "MA"
                postalCode = "12345"
            }
        }
}

Create an Asymmetric Object

An asymmetric object is an insert-only object. When you create an AsymmetricRealmObject, it syncs unidirectionally via Data Ingest to the Atlas database linked to your Atlas App Services App. You cannot access an AsymmetricRealmObject locally, add it to or remove it from a realm, or query for it. For more information, see Asymmetric Objects.

You must create an AsymmetricRealmObject using the insert() extension method within a write transaction:

realm.write {
    insert(WeatherSensor().apply {
        deviceId = "WX1278UIT"
        temperatureInFarenheit = 6.7F
        barometricPressureInHg = 29.65F
        windSpeedInMph = 2
    })
}

You can create asymmetric objects for a realm initialized with a Flexible Sync SyncConfiguration. For more information, see Open the synced Realm with a Flexible Sync configuration.