Realm React
Build better apps, faster.
Introduction
Setting up Realm in a React Native application has historically been complex. Re-rendering of components when objects in the database change requires manually adding and removing listeners, which produce a lot of boilerplate code and is error-prone (if listeners properly removed on unmount). This library alleviates that by providing React hooks which return Realm data that is state aware. As a consequence, any change to the Realm data will cause components using the hook to re-render.
Documentation for @realm/react and Realm can be found at docs.mongodb.org.
Installation
This library requires react-native >= 0.59 and realm >= 11
npm:
npm install realm @realm/react
yarn:
yarn add realm @realm/react
Try it out
Here is a simple task manager application written with Realm React. Copy into a React Native application and give it a try!
import React, { useState } from "react";
import { SafeAreaView, View, Text, TextInput, FlatList, Pressable } from "react-native";
import { Realm, RealmProvider, useRealm, useQuery } from '@realm/react'
class Task extends Realm.Object {
_id!: Realm.BSON.ObjectId;
description!: string;
isComplete!: boolean;
createdAt!: Date;
static generate(description: string) {
return {
_id: new Realm.BSON.ObjectId(),
description,
createdAt: new Date(),
};
}
static schema = {
name: 'Task',
primaryKey: '_id',
properties: {
_id: 'objectId',
description: 'string',
isComplete: { type: 'bool', default: false },
createdAt: 'date'
},
};
}
export default function AppWrapper() {
return (
<RealmProvider schema={[Task]}><TaskApp /></RealmProvider>
)
}
function TaskApp() {
const realm = useRealm();
const tasks = useQuery(Task);
const [newDescription, setNewDescription] = useState("")
return (
<SafeAreaView>
<View style={{ flexDirection: 'row', justifyContent: 'center', margin: 10 }}>
<TextInput
value={newDescription}
placeholder="Enter new task description"
onChangeText={setNewDescription}
/>
<Pressable
onPress={() => {
realm.write(() => {
realm.create("Task", Task.generate(newDescription));
});
setNewDescription("")
}}><Text>➕</Text></Pressable>
</View>
<FlatList data={tasks.sorted("createdAt")} keyExtractor={(item) => item._id.toHexString()} renderItem={({ item }) => {
return (
<View style={{ flexDirection: 'row', justifyContent: 'center', margin: 10 }}>
<Pressable
onPress={() =>
realm.write(() => {
item.isComplete = !item.isComplete
})
}><Text>{item.isComplete ? "✅" : "☑️"}</Text></Pressable>
<Text style={{ paddingHorizontal: 10 }} >{item.description}</Text>
<Pressable
onPress={() => {
realm.write(() => {
realm.delete(item)
})
}} ><Text>{"🗑️"}</Text></Pressable>
</View>
);
}} ></FlatList>
</SafeAreaView >
);
}For a full fledged example, check out our templates.
Realm Hooks
useRealm
Returns the instance of the Realm configured by createRealmContext and the RealmProvider. The following is an example of how to use this Hook to make a write transaction callback for a component.
import {useRealm} from '@realm/react';
// assume props contain item a Realm.Object
const Component = ({item}) => {
const realm = useRealm();
const toggleComplete = useCallback((item) => {
realm.write(() => {
item.isComplete = !item.isComplete
})
},[item, realm])
return (
<Pressable
onPress={() =>
realm.write(() => {
item.isComplete = !item.isComplete
})
}><Text>{item.isComplete ? "✅" : "☑️"}</Text>
</Pressable>
)
}useQuery
Returns Realm.Results from a given type. This Hook will update on any changes to any Object in the Collection and return an empty array if the Collection is empty.
The result of this can be consumed directly by the data argument of any React Native VirtualizedList or FlatList. If the component used for the list's renderItem prop is wrapped with React.Memo, then only the modified object will re-render.
import {useQuery} from '@realm/react';
const Component = () => {
// ObjectClass is a class extending Realm.Object, which should have been provided in the Realm Config.
// It is also possible to use the model's name as a string ( ex. "Object" ) if you are not using class based models.
const sortedCollection = useQuery(ObjectClass, (collection) => {
// The methods `sorted` and `filtered` should be passed as a `query` function.
// Any variables that are dependencies of this should be placed in the dependency array.
return collection.sorted();
}, []);
return (
<FlatList data={sortedCollection} renderItem={({ item }) => <Object item={item}/>
)
}useObject
Returns a Realm.Object for a given type and primary key. The Hook will update on any changes to the properties on the returned Object and return null if it either doesn't exist or has been deleted.
import {useObject} from '@realm/react';
const Component = ({someId}) => {
// ObjectClass is a class extending Realm.Object, which should have been provided in the Realm Config.
// It is also possible to use the model's name as a string ( ex. "Object" ) if you are not using class based models.
const object = useObject(ObjectClass, someId);
return (
<View>
<Text>{object.name}</Text>
</View>
)
}Setting Things Up
RealmProvider
To get started with @realm/react, one must wrap your app with a RealmProvider. The RealmProvider can be configured using props. At a minimum, one must set the schema prop to the Realm models that they have configured.
Any child of the RealmProvider will be able to use the hooks to access and manipulate Realm data. Here is an example of how to setup Realm React with a Task model:
import { RealmProvider, useQuery, Realm } from '@realm/react';
const AppWrapper = () => {
return (
<RealmProvider schema={[Item]}>
<SomeComponent/>
<RealmProvider>
)
}
const SomeComponent = () => {
const items = useQuery(Item)
//..
}The RealmProvider also comes with a fallback prop that is rendered when while awaiting for the Realm to open. For local Realm, this is instant, but for synced a Realm, it can take time for larger datasets to sync, especially if it's the first time the app has been opened. In that case, it is recommended to provide a loading component as a fallback.
const AppWrapper = () => {
return (
<RealmProvider fallback={<Loading/>} >
<App/>
<RealmProvider>
)
}In some cases, it may be necessary to access the configured Realm from outside of the RealmProvider, for instance, implementing a client reset fallback. This can be done by creating a ref with useRef and setting the realmRef property of RealmProvider.
const AppWrapper = () => {
const realmRef = useRef<Realm|null>(null)
return (
<RealmProvider realmRef={realmRef}>
<App/>
<RealmProvider>
)
}It may also be necessary to render multiple RealmProviders of the same Realm in an app. In this case, the flag closeOnUnmount can be set to false`` to prevent both Realm instances from closing when one has been removed from the component tree. This is set to true` by default.
const AppWrapper = () => {
return (
<RealmProvider closeOnUnmount={false}>
<App/>
<RealmProvider>
)
}Dynamically Updating a Realm Configuration
It is possible to update the realm configuration by setting props on the RealmProvider. The RealmProvider takes props for all possible realm configuration properties.
For example, one could setup the sync configuration based on a user state:
const [user, setUser] = useState()
//... some logic to get user state
<RealmProvider sync={{ user, partition }}>
useApp and the AppProvider
The useApp hook can be used to access your Realm App instance as long as the AppProvider wraps your application. This should be done outside of your RealmProvider.
AppProvider usage:
import { AppProvider } from '@realm/react'
//...
// Wrap your RealmProvider with the AppProvider and provide an appId
<AppProvider id={appId}>
<RealmProvider sync={{user, flexible: true}}>
//...
</RealmProvider>
</AppProvider>useApp usage:
// Access the app instance using the useApp hook
import { useApp } from '@realm/react'
const SomeComponent = () => {
const app = useApp();
//...
}It is also possible to receive a reference to the app outside of the AppProvider, through the appRef property. This must be set to a React reference returned from useRef.
const AppWrapper = () => {
const appRef = useRef<Realm.App|null>(null)
return (
<AppProvider appRef={appRef}>
<App/>
<AppProvider>
)
}
useUser and the UserProvider
With the introduction of the UserProvider, the user can be automatically populated into the underlying Realm configuration. The fallback property can be used to provide a login component.
The child components will be rendered as soon as a user has authenticated. On logout, the fallback will be displayed again.
UserProvider usage:
import { AppProvider, UserProvider } from '@realm/react'
//...
<AppProvider id={appId}>
<UserProvider fallback={LoginComponent}>
{/* After login, user will be automatically populated in realm configuration */}
<RealmProvider sync={{flexible: true}}>
//...
</RealmProvider>
</UserProvider>
</AppProvider>useUser usage:
// Access the app instance using the useApp hook
import { useUser } from '@realm/react'
const SomeComponent = () => {
const user = useUser();
//...
}Authentication Hooks
The following hooks can be used to authenticate users in your application. They return authentication operations and a single result object which can be read to track the progress of the current result. More information about the specific auth methods can be found in the Authenticate Users Documentation.
result
The authentication hooks return a result has the following structure:
{
/**
* The current state of the operation.
* Enumerated by OperationState
*/
state, // "not-started", "pending", "success", "error"
/**
* The string name of the current operation running.
*/
operation,
/**
* Convenience accessors, so users can write e.g. `loginResult.pending`
* instead of `loginResult.state === OperationState.Pending`
*/
pending, // true or false
success, // true or false
/**
* The error returned from the operation, if any. This will only be populated
* if `state === OperationState.Error`, and will be cleared each time the
* operation is called.
*/
error // Error based object or undefined
}useAuth
These hooks would typically be used in the fallback component of the UserProvider
This can be used to manage the state of the current login operation.
logIn
Log in with a Realm.Credentials instance. This allows login with any authentication mechanism supported by Realm. If this is called when a user is currently logged in, it will switch the user.
const {logIn, result} = useAuth();
// Log in with a `Realm.Credentials` instance. This allows login with any authentication mechanism supported by Realm.
// If this is called when a user is currently logged in, it will switch the user.
// Typically the other methods from `useAuth` would be used.
// If this is rendered in the fallback of the `UserProvider`,
// then it's children will be rendered as soon as this succeeds.
useEffect( () => logIn(Realm.Credential.anonymous()), [] );
}
if(result.pending) {
return (<LoadingSpinner/>)
}
if(result.error) {
return (<ErrorComponent/>)
}
if(result.success) {
return (<SuccessComponent/>)
}
//...logInWithAnonymous
Log in with the Anonymous authentication provider.
const {logInWithAnonymous, result} = useAuth();
const performLogin = () => {
logInWithAnonymous();
};logInWithApiKey
Log in with an API key.
const {logInWithApiKey, result} = useAuth();
const performLogin = () => {
const key = getApiKey(); // user defined function
logInWithApiKey(key);
};logInWithEmailPassword
Log in with Email/Password.
const {logInWithEmailPassword, result} = useAuth();
const [email, setEmail] = useState("");
const [password, setPassword] = useState("");
const performLogin = () => {
logInWithEmailPassword({email, password});
};logInWithJWT
Log in with a JSON Web Token (JWT).
const {logInWithJWT, result} = useAuth();
const performLogin = () => {
const token = authorizeWithCustomerProvider(); // user defined function
logInWithJWT(token);
};logInWithGoogle
Log in with Google.
const {logInWithGoogle, result} = useAuth();
const performLogin = () => {
const token = getGoogleToken(); // user defined function
logInWithGoogle({idToken: token});
};logInWithApple
Log in with Apple.
const {logInWithApple, result} = useAuth();
const performLogin = () => {
const token = getAppleToken(); // user defined function
logInWithApple(token);
};logInWithFacebook
Log in with Facebook.
const {logInWithFacebook, result} = useAuth();
const performLogin = () => {
const token = getFacebookToken(); // user defined function
logInWithFacebook(token);
};logInWithCustomFunction
Log in with a custom function.
const {logInWithFunction, result} = useAuth();
const performLogin = () => {
const customPayload = getAuthParams(); // user defined arguments
logInWithFunction(customPayload);
};logOut
Log out the current user. This will immediately cause the fallback from the UserProvider to render.
const {logOut, result} = useAuth();
const performLogOut = () => {
logOut();
};useEmailPasswordAuth
This hook is similar to useAuth, but specifically offers operations around Email/Password authentication. This includes methods around resetting passwords and confirming users. It returns the same result object as useAuth.
logIn
Convenience function to log in a user with an email and password - users
could also call logIn(Realm.Credentials.emailPassword(email, password)). @returns A Realm.User` instance for the logged in user.
const {logIn, result} = useEmailPasswordAuth();
const [email, setEmail] = useState("");
const [password, setPassword] = useState("");
const performLogin = () => {
logIn({email, password});
};
if(result.pending) {
return (<LoadingSpinner/>)
}
if(result.error) {
return (<ErrorComponent/>)
}
if(result.success) {
return (<SuccessComponent/>)
}
//...register
Register a new user.
const {register, result} = useEmailPasswordAuth();
const [email, setEmail] = useState("");
const [password, setPassword] = useState("");
const performRegister = () => {
register({email, password});
};confirm
Confirm a user's account by providing the token and tokenId received.
const {confirm, result} = useEmailPasswordAuth();
const performConfirmation = () => {
confirm({token, tokenId});
};resendConfirmationEmail
Resend a user's confirmation email.
const {resendConfirmationEmail, result} = useEmailPasswordAuth();
const [email, setEmail] = useState("");
const performResendConfirmationEmail = () => {
resendConfirmationEmail({email});
};retryCustomConfirmation
Retry the custom confirmation function for a given user.
const {retryCustomConfirmation, result} = useEmailPasswordAuth();
const [email, setEmail] = useState("");
const performRetryCustomConfirmation = () => {
retryCustomConfirmation({email});
};sendResetPasswordEmail
Send a password reset email for a given user.
const {sendResetPasswordEmail, result} = useEmailPasswordAuth();
const [email, setEmail] = useState("");
const performSendResetPasswordEmail = () => {
sendResetPasswordEmail({email});
};resetPassword
Complete resetting a user's password.
const {resetPassword, result} = useEmailPasswordAuth();
const [password, setPassword] = useState("");
const performResetPassword = () => {
resetPassword({token, tokenId, password});
};callResetPasswordFunction
Call the configured password reset function, passing in any additional arguments to the function.
const {callResetPasswordFunction, result} = useEmailPasswordAuth();
const [email, setEmail] = useState("");
const [password, setPassword] = useState("");
const performResetPassword = () => {
callRestPasswordFunction({email, password}, "extraArg1", "extraArg2");
};logOut
Log out the current user.
const {logOut, result} = useEmailPasswordAuth();
const performLogout = () => {
logOut();
}Multiple Realms
createRealmContext can be used to create a contextualized hooks and a RealmProvider to the passed in configuration for a Realm. It can be called multiple times if your app requires more than one Realm. In that case, you would have multiple RealmProviders that wrap your app and must use the hooks from the created context you wish to access.
The Context object will contain a RealmProvider, which will a open a Realm when it is rendered. It also contains a set of hooks that can be used by children to the RealmProvider to access and manipulate Realm data.
The structure of the Context object is:
{
RealmProvider, // Wrapper for your application to enable usage of hooks
useRealm, // Hook to access the configured Realm
useQuery, // Hook to access collections of Realm objects
useObject, // Hook to access a single Realm object by primary key
}
The configuration for the Realm context can be given as an object argument to createRealmContext or be set directly on the RealmProvider props. The props set on RealmProvider will be merged with those provided to createRealmContext, with the props taking priority. A Realm will be opened with this merged configuration when the Realm Context Provider is rendered. A fallback component can optionally be rendered until the Realm is opened. This is useful for projects using Realm Sync.
const { RealmProvider: PublicRealmProvider, useRealm: usePublicRealm, useObject: usePublicObject, useQuery: usePublicQuery } = createRealmContext(publicConfig);
const { RealmProvider: PrivateRealmProvider, useRealm: usePrivateRealm, useObject: usePrivateObject, useQuery: usePrivateQuery } = createRealmContext(privateConfig);It is also possible to call it without any Config; in the case that you want to do all your configuration through the RealmProvider props.
Sync Debug Logs
When running into issues with sync, it may be helpful to view logs in order to determine what the issue was or to provide more context when submitting an issue. This can by done with the AppProvider.
// logger includes a default that prints level and message
<AppProvider id={appId} logLevel={'trace'} logger={(level, message) => console.log(`[${level}]: ${message}`)}>