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Caching MWA Authorization

A key component to unlocking great UX in mobile dApps is correctly storing the address and authentication token of a user's currently authorized wallet.

If authorization details are cached, then it can be re-used between reloads of the dApp (i.e: Staying "connected" after exiting and reopening the app).

Simple Storage API​

This guide will cover a simple storage API to manage authorization details in a dApp using the @react-native-async-storage/async-storage library.

AsyncStorage​

Install it with:

yarn add @react-native-async-storage/async-storage

You can use it like this:

import AsyncStorage from '@react-native-async-storage/async-storage';

// Store a string against some key.
await AsyncStorage.setItem('address', 'abc123');
// Then, some time later...
const storedAddress = await AsyncStorage.getItem('address');

Implementation Examples​

Check for cached authorization​

When the dApp boots up, we first check the cache to see if there is a prior authorization. We designate the cache keys to be authToken and base64Address.

const App = () => {
    // Store details about the currently connected wallet.
    const [currentAccount, setCurrentAccount] = useState<{
        authToken: string;
        pubkey: PublicKey;
    } | null>(null);
    
    // When the application boots up, check to see if we have a prior authorization.
    useEffect(() => {
        (async () => {
            const [cachedAuthToken, cachedBase64Address] = await Promise.all([
                AsyncStorage.getItem('authToken'),
                AsyncStorage.getItem('base64Address'),
            ]);
            if (cachedBase64Address && cachedAuthToken) {
                const pubkeyAsByteArray = toByteArray(cachedBase64Address);
                const cachedCurrentAccount = {
                    authToken: cachedAuthToken,
                    pubkey: new PublicKey(pubkeyAsByteArray),
                };
                setCurrentAccount(cachedCurrentAccount);
            }
        })();
    }, []);

    /* ...*/
}

Cache on authorize​

You can cache the authorization details, when the user completes an authorize request with wallet. In this example, the caches when the connect button is pressed.

// Store details about the currently connected wallet.
const [currentAccount, setCurrentAccount] = useState<{
    authToken: string;
    pubkey: PublicKey;
} | null>(null);

const handleConnectPress = useCallback(() => {
    transact(async wallet => {
        const {accounts, auth_token} = await wallet.authorize({
            cluster: 'devnet',
            identity: {
                name: 'My amazing app',
            },
        });
        const firstAccount = accounts[0];
        AsyncStorage.setItem('authToken', auth_token);
        AsyncStorage.setItem('base64Address', firstAccount.address);
        const pubkeyAsByteArray = toByteArray(firstAccount.address);
        const nextCurrentAccount = {
            authToken: auth_token,
            pubkey: new PublicKey(pubkeyAsByteArray),
        };
        setCurrentAccount(nextCurrentAccount);
    });
}, []);

We can choose to only render the Connect button, if there is no currentAccount state.

Clear cache on deauthorize​

The user can choose to "disconnect" their wallet with the deauthorize MWA request. In this case, we should invalidate the cache by calling AsyncStorage.clear().

// Pressing disconnect deauthorizes this app with the wallet, and clears
// all cached account information.
const handleDisconnectPress = useCallback(() => {
    transact(async wallet => {
        if (currentAccount == null) {
            throw new Error('There is no current account to deauthorize');
        }
        await wallet.deauthorize({auth_token: currentAccount.authToken});
        AsyncStorage.clear();
        setCurrentAccount(null);
    });
}, [currentAccount]);

Reference Apps​

The following reference apps showcase implementing MWA authorization in a dApp.

SimpleStorageDapp​

This reference app makes a small change to the Solana Mobile dApp Scaffold adding an authorization cache with AsyncStorage. The current authorization is managed through the AuthorizationProvider component.

example-react-native-app​

This reference app implements an AsyncStorage provider with the swr data fetching library. The caching and parsing logic is defined in App component while the current authorization is provided with the useAuthorization hook.