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Quick Start - React Native SDK

On this page

  • About the @realm/react Package
  • Set Up Your Realm App
  • Define Object Models
  • Configure a Realm
  • Work With Realm Objects
  • Read, Sort, and Filter Objects
  • Create, Update, and Delete Realm Objects
  • Add Atlas Device Sync (Optional)
  • Prerequisites
  • Configure and Access a Synced Realm
  • Next: Check out the Template Apps and Tutorial

This page demonstrates how to use Realm using the React Native SDK.

Before you begin, install the Realm React Native SDK.

About the @realm/react Package

@realm/react is a package used in the React Native SDK. It provides state-aware React hooks for Realm data. The hooks watch the Realm data and re-render components as needed.

The React Native SDK documentation uses the @realm/react npm package for examples and describing concepts.

Refer to these pages for more details:

Set Up Your Realm App

After installing the realm and @realm/react packages, there are a few more things to set up before you can access your realm and work with local data:

  • Define your object models

  • Configure a realm by creating a realm context object, extracting hooks, and setting up providers

Define Object Models

Your application's object models define the data types that you can store within a realm. Each object model becomes a Realm object type.

To define a Realm object model:

  1. Create a class that extends Realm.Object.

  2. Add a schema field.

  3. For the schema value, create an object that contains properties and name properties. The name value must be unique among object types in your realm.

// Define your object model
export class Profile extends Realm.Object<Profile> {
  _id!: BSON.ObjectId;
  name!: string;
  static schema: ObjectSchema = {
    name: 'Profile',
    properties: {
      _id: 'objectId',
      name: {type: 'string', indexed: 'full-text'},
    },
    primaryKey: '_id',
  };
}

To learn more, refer to Define a Realm Object Model.

Configure a Realm

Before you can work with data, you need to configure a realm. This means you need to set up context and providers from @realm/react. To learn more, refer to Configure a Realm.

To configure and access a local realm:

  1. Import RealmProvider from @realm/react.

  2. Pass your object models to the schema prop.

  3. Add other Configuration object properties as props to RealmProvider.

import React from 'react';
import {RealmProvider} from '@realm/react';
// Import your models
import {Profile} from '../../../models';
export const AppWrapper = () => {
  return (
    <RealmProvider schema={[Profile]}>
      <RestOfApp />
    </RealmProvider>
  );
};

Work With Realm Objects

After you have a data model and a configured realm, you can create, read, update, or delete Realm objects.

You must nest components that perform these operations inside of RealmProvider. The useRealm(), useQuery(), and useObject() hooks enable you to perform read and write operations in your realm.

For detailed descriptions of RealmProvider and its hooks, refer to RealmProvider (@realm/react)

Read, Sort, and Filter Objects

@realm/react provides hooks to help you find a collection of Realm objects or a single Realm object.

As part of useQuery(), you can filter or sort the results using Realm Query Language (RQL).

import React from 'react';
import {useQuery} from '@realm/react';
import {Profile} from '../../models';
export const Read = () => {
  // Find
  const profiles = useQuery(Profile);
  // Sort
  const sortedProfiles = useQuery(Profile, profiles => {
    return profiles.sorted('name', false);
  });
  // Filter
  const filteredProfiles = useQuery(Profile, profiles => {
    return profiles.filtered('name == "testProfile"');
  });
  // ... rest of component
};

To learn more, refer to CRUD - Read and Query Data.

Read Operations Outside of hooks

Sometimes, you may need to use Realm read operations, but not at the top level of your React Native component. Because hooks only work at the top level of components, you can't use the @realm/react hooks in these situations.

Instead, you can use Realm.objects for collections or Realm.objectForPrimaryKey a single object.

Create, Update, and Delete Realm Objects

After accessing the realm with useRealm(), you can create, update, and delete objects inside of the realm. All operations must be in a Realm.write() transaction block.

To learn more, refer to Write Transactions.

Create Objects

To create a new Realm object, specify the object type, pass in the object's initial values, and add it to the realm in a write transaction block.

import React, {useState} from 'react';
import {Text, TextInput, View} from 'react-native';
import {BSON} from 'realm';
import {useRealm} from '@realm/react';
import {Profile} from '../../models';
export const Create = () => {
  const realm = useRealm();
  const [profileName, setProfileName] = useState('');
  const addProfile = () => {
    realm.write(() => {
      realm.create(Profile, {
        _id: new BSON.ObjectId(),
        name: profileName,
      });
    });
  };
  return (
    <View>
      <Text>Create</Text>
      <TextInput
        onChangeText={setProfileName}
        value={profileName}
        placeholder="Profile name..."
      />
      <Button
        title="Add Profile"
        onPress={addProfile}
      />
    </View>
  );
};

To learn more, refer to CRUD - Create.

Update Objects

To update a Realm object, update its properties in a write transaction block.

import React, {useState} from 'react';
import {Text, FlatList, View, Pressable, TextInput} from 'react-native';
import {useRealm, useQuery} from '@realm/react';
import {Profile} from '../../models';
export const Update = () => {
  const realm = useRealm();
  const profiles = useQuery(Profile);
  const [profileToUpdate, setProfileToUpdate] = useState('');
  const [newProfileName, setNewProfileName] = useState('');
  const updateProfile = () => {
    const toUpdate = realm
      .objects(Profile)
      .filtered('name == $0', profileToUpdate);
    realm.write(() => {
      toUpdate[0].name = newProfileName;
    });
  };
  return (
    <View>
      <Text>Update</Text>
      {profiles.length ? (
        <View>
          <Text>Profiles: </Text>
          <FlatList
            scrollEnabled={false}
            data={profiles}
            horizontal={true}
            renderItem={({item}) => (
              <Pressable
                onPress={() => {
                  setProfileToUpdate(item.name);
                }}>
                <Text
                 >
                  {item.name}
                </Text>
              </Pressable>
            )}
            keyExtractor={item => item.name}
          />
        </View>
      ) : (
        <Text>🛑 No profiles found</Text>
      )}
      {profileToUpdate && (
        <TextInput
          style={styles.textInput}
          onChangeText={setNewProfileName}
          value={newProfileName}
          placeholder="New profile name..."
        />
      )}
      <Button
        title="Update profile"
        onPress={updateProfile}
      />
    </View>
  );
};

To learn more, refer to CRUD - Update.

Delete Objects

To delete a Realm object, pass the object to Realm.delete() within a write transaction block.

import React, {useState} from 'react';
import {Text, FlatList, View, Pressable} from 'react-native';
import {useRealm, useQuery} from '@realm/react';
import {Profile} from '../../models';
export const Delete = () => {
  const realm = useRealm();
  const profiles = useQuery(Profile);
  const [profileToDelete, setProfileToDelete] = useState('');
  const deleteProfile = () => {
    const toDelete = realm
      .objects(Profile)
      .filtered('name == $0', profileToDelete);
    realm.write(() => {
      realm.delete(toDelete);
    });
  };
  return (
    <View>
      <Text>Delete</Text>
      {profiles.length ? (
        <View>
          <Text>Profiles: </Text>
          <FlatList
            scrollEnabled={false}
            data={profiles}
            horizontal={true}
            renderItem={({item}) => (
              <Pressable
                onPress={() => {
                  setProfileToDelete(item.name);
                }}>
                <Text
                 >
                  {item.name}
                </Text>
              </Pressable>
            )}
            keyExtractor={item => item.name}
          />
        </View>
      ) : (
        <Text>🛑 No profiles found</Text>
      )}
      <Button
        title="Delete profile"
        onPress={deleteProfile}
      />
    </View>
  );
};

To learn more, refer to CRUD - Delete.

Add Atlas Device Sync (Optional)

After getting your non-sync realm running, you can add Atlas Device Sync. This enables your realm data to sync with a MongoDB Atlas cluster and other client devices.

To use Device Sync, you need to set up a couple more things:

  • Create a backend in Atlas App Services (see the prerequisites below)

  • Configure a Flexible Sync realm instead of a non-sync realm

Prerequisites

Configure and Access a Synced Realm

To use a Device Sync, you need to configure three @realm/react providers:

After you initialize your App, authenticate a user, and define your object model, you can configure a synced realm. This is similar to configuring a local realm. However, you need to add some additional props to the RealmProvider.

Add the sync prop to RealmProvider and pass it a FlexibleSyncConfiguration object. This sync object must contain flexible: true You should also add initial subscriptions. You must have at least one sync subscription before you can read or write synced data.

To configure and access a synced realm:

  1. Initialize the App using AppProvider. You can find your App ID in the App Services UI.

  2. Authenticate a User with UserProvider

  3. Configure a synced realm with RealmProvider

import React from 'react';
import {Credentials} from 'realm';
import {RealmProvider, AppProvider, UserProvider, useApp} from '@realm/react';
// Import your models
import {Profile} from '../../../models';
// Expose a sync realm
export function AppWrapperSync() {
  return (
    <AppProvider id={APP_ID}>
      <UserProvider fallback={LogIn}>
        <RealmProvider
          schema={[Profile]}
          sync={{
            flexible: true,
            onError: (_session, error) => {
              console.log(error);
            },
            initialSubscriptions: {
              update(subs, realm) {
                subs.add(realm.objects('Profile'));
              },
              rerunOnOpen: true,
            },
          }}
          fallback={fallback}>
          <RestOfApp />
        </RealmProvider>
      </UserProvider>
    </AppProvider>
  );
}

The syntax to create, read, update, and delete objects in a synced realm is identical to the syntax for non-synced realms. While you work with local data, a background thread efficiently integrates, uploads, and downloads changesets.

To learn more, refer to Configure a Synced Realm.

Next: Check out the Template Apps and Tutorial

If you are interested in a guided experience, you can read our Realm React Native SDK tutorial. This tutorial implements and expands on a base React Native app built with Realm and Device Sync.

You could also use the template app to experiment with the React Native SDK on your own. To set up the template app, refer to Template Apps in the Atlas App Services documentation.

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