Skip to main content

How to update data in Realm Database in Kotlin

How to update data in Realm Database in Kotlin.

Realm is a mobile database that provides a simple and efficient way to store and manage data in mobile applications. In this tutorial, we will learn how to update data in a Realm database using Kotlin.

Step 1: Set Up Realm in Your Project

Before we can start updating data in a Realm database, we need to set up Realm in our project. Follow these steps to set up Realm in your Kotlin project:

  1. Add the following dependencies to your project's build.gradle file:
repositories {

dependencies {
implementation 'io.realm:realm-gradle-plugin:10.8.0'
implementation 'io.realm:realm-kotlin-extensions:10.8.0'
  1. Apply the Realm plugin in your app's build.gradle file:
apply plugin: 'realm-android'
  1. Sync your project to download the required dependencies.

Step 2: Define a Realm Object Model

To update data in a Realm database, we need to define a Realm object model that represents the data we want to store. Each object in the Realm database will be an instance of this model.

For example, let's say we want to store information about books. We can define a Book class as follows:

import io.realm.RealmObject
import io.realm.annotations.PrimaryKey

open class Book : RealmObject() {
var id: Int = 0
var title: String = ""
var author: String = ""
var year: Int = 0

In this example, we have defined a Book class with properties id, title, author, and year. The @PrimaryKey annotation is used to mark the id property as the primary key for the object.

Step 3: Update Data in the Realm Database

Now that we have set up Realm and defined our object model, we can start updating data in the Realm database.

To update data in Realm, follow these steps:

  1. Open a Realm instance by calling Realm.getDefaultInstance():
val realm = Realm.getDefaultInstance()
  1. Begin a write transaction:
  1. Retrieve the object from the database that you want to update. You can use Realm queries to fetch the object based on specific criteria. For example, to update a book with a specific id, you can use the following query:
val book = realm.where("id", 1).findFirst()
  1. Update the properties of the retrieved object:
book?.title = "New Title"
book?.author = "New Author"
book?.year = 2022
  1. Commit the write transaction:
  1. Close the Realm instance:

That's it! The data in the Realm database has been updated.

Example: Updating a Book in the Realm Database

Let's put all the steps together and see an example of updating a book in the Realm database:

fun updateBook(bookId: Int, newTitle: String, newAuthor: String, newYear: Int) {
val realm = Realm.getDefaultInstance()

val book = realm.where("id", bookId).findFirst()
book?.title = newTitle
book?.author = newAuthor
book?.year = newYear


In this example, we have defined a function updateBook that takes the bookId, newTitle, newAuthor, and newYear as parameters. It opens a Realm instance, begins a write transaction, retrieves the book with the specified bookId, updates its properties, commits the transaction, and closes the Realm instance.

You can call this function with the appropriate arguments to update a book in the Realm database.


In this tutorial, we have learned how to update data in a Realm database using Kotlin. We set up Realm in our project, defined a Realm object model, and performed the necessary steps to update data in the Realm database.