Introduction to Realm

What Problem Does Realm Solve?

Mobile developers face a number of unique challenges. You must:

• Handle the unpredictable environment of mobile apps. Connections can be lost, devices can shut down at any time, and clients often update long after release.

• Maintain common data schemas and APIs between mobile clients, backend APIs, and databases.

• Stay aware of security vulnerabilities across all components in an ecosystem.

• Consistently serialize objects between networks, database storage, and application memory.

• Program in the languages and frameworks for one or more mobile operating systems.

All of these challenges present different obstacles. You can solve each in isolation with a wide variety of libraries and frameworks. Deciding the right solution for each problem with the right tradeoffs is a challenge mobile developers know all too well.

The combination of multiple environments creates even more challenges. For instance, you can use a Java library on your Android client to serialize objects, but that library likely wouldn't work on iOS. And this doesn't even take into account consistency across backend services.

Realm Database

Many of these challenges arise due to particularities of the mobile environment. These challenges include network reliability, local storage, and keeping UIs reactive. Realm Database solves many common mobile programming headaches:

• Local storage: Realm Database runs right on client devices. Access objects using the native query language for each platform. Storing, accessing, and updating your data is simple and lightweight.

• Network reliability: Realm Database is offline-first. You always read from and write to the local database, not over the network. When Device Sync is enabled, Realm Database synchronizes data with App Services over the network in a background thread. The sync protocol resolves conflicts consistently on each client and in the linked Atlas cluster.

• Reactive UI: Live objects always reflect the latest data stored in Realm Database. You can subscribe to changes, letting you keep your UI consistently up to date.

The Realm SDKs connect to local realms for Android, iOS, Node.js, React Native, Flutter, and UWP development.

Sync Data with MongoDB Atlas

Client applications generate a lot of data. Whether it's uploaded reviews and ratings, posts and comments on a blog, or inventory in a kitchen, you need to store that data somewhere.

The Realm SDKs use Atlas Device Sync to synchronize app data between clients and MongoDB Atlas. Atlas Device Sync handles network access and conflict resolution in a background thread of your application, so your application logic stays the same regardless of network conditions.

Once your client data is in Atlas, you can leverage the full Atlas developer data platform. Perform aggregations and other complex workloads with the full capabilities of MongoDB. Or connect your Atlas instance to Charts to visualize your data in real time. Storing your data in Atlas makes it easy to share data across users and platforms.

Use Atlas App Services

The Realm SDKs integrate with App Services to easily and securely work with data from your app:

• Query MongoDB Atlas directly from the Realm SDKs using built-in MongoDB interfaces. You can also configure the Atlas Data API to query MongoDB using an HTTP client in your app.

• App Services Users and Authentication provide built-in user management. Integrate with a JWT authentication service or directly with third-party authentication providers, like Facebook, Google, and Apple.

• Atlas Triggers automatically execute an Atlas Function at a scheduled time or when an event occurs, such as a change to a MongoDB database in Atlas or a user logs in.

• The Atlas GraphQL API accesses data stored in a linked MongoDB cluster with a standard GraphQL client.

• App Services Rules control who accesses what data.

• App Services Values and Secrets define global variables and private credentials once and use them across your entire App.

Get Started with Realm

Check out our Task Tracker tutorial for any of these platforms:

• Android with Kotlin

• iOS with Swift

• React Native with JavaScript

• Xamarin (iOS and Android) with C#

Or start by experimenting with a working Sync-enabled client application with a template app.

You can also refer to the documentation for each client SDK:

• Flutter SDK for Flutter

• Java SDK for Java

• Kotlin SDK for Kotlin

• .NET SDK for C# and Xamarin

• Node.js SDK for Node.js

• React Native SDK for TypeScript and JavaScript with React Native

• Swift SDK for Swift and Objective-C

• Web SDK for browser JavaScript

Summary

• Realm Database is an offline-first mobile object database in which you can directly access and store live objects without an ORM.

• Live Objects always reflect the latest state of data in the database, which simplifies keeping your UI in sync with changes to your data.

• Atlas Device Sync synchronizes data between client-side realms and the server-side MongoDB Atlas cluster linked to your app. Realm Database synchronizes data in a background thread, abstracting away network usage so you don't have to worry about latency or dropped connections.

• The Realm SDKs integrate with App Services to easily and securely work with your data in Atlas.