React Native Firebase: how to check authorization? - firebase

Question

After calling "createUserWithEmailAndPassword" or "signInWithEmailAndPassword", a property "currentUser" becomes filled in "auth()". It remains full after restarting an application, even if I remove this user from the Firebase console.
How can I check user's authorization when the application starts?

Answer 1

To force the client to "check in" with the server, you would use the User#getIdToken() method by calling firebase.auth().currentUser.getIdToken(true). If the user has been deleted, this should reject with the error code 'auth/user-token-expired'.
From the React Native Firebase Quick Start documentation, I'll use this as the base of the MWE:
import React, { useState, useEffect } from 'react';
import { View, Text } from 'react-native';
import auth from '#react-native-firebase/auth';
function App() {
// Set an initializing state whilst Firebase connects
const [initializing, setInitializing] = useState(true);
const [user, setUser] = useState();
// Handle user state changes
function onAuthStateChanged(user) {
setUser(user);
if (initializing) setInitializing(false);
}
useEffect(() => {
const subscriber = auth().onAuthStateChanged(onAuthStateChanged);
return subscriber; // unsubscribe on unmount
}, []);
if (initializing) return null;
if (!user) {
return (
<View>
<Text>Login</Text>
</View>
);
}
return (
<View>
<Text>Welcome {user.email}</Text>
</View>
);
}
Once the user has logged in or their cached access has been restored, onAuthStateChanged will receive an event with the current user object. Here we add the ID token request.
function onAuthStateChanged(user) {
if (!user) {
// not logged in
setUser(user);
if (initializing) setInitializing(false);
return;
}
user.getIdToken(/* forceRefresh */ true)
.then(token => {
// if here, this user is still authorised.
setUser(user);
if (initializing) setInitializing(false);
}, error => {
if (error.code === 'auth/user-token-expired') {
// token invalidated. No action required as onAuthStateChanged will be fired again with null
} else {
console.error('Unexpected error: ' + error.code);
}
});
}