Authentication listeners when refactoring to React hooks - reactjs

Question

I'm having a little trouble figuring out how to change my authentication handling component when refactoring from a React class to React hooks.
Here's the relavant code in my class:
state = {
user: null
}
componentDidMount() {
authGetUser(user => {
if (user !== this.state.user) {
this.setState({user})
}
})
}
componentWillUnmount() {
authUnsubscribe()
}
handleAuthClick = () => {
if (this.state.user) {
authSignOut()
} else {
authSignIn()
}
}
And here it is with hooks:
const [user, setUser] = useState<firebase.User | null>(null)
useEffect(() => {
return authUnsubscribe() // runs on mount and unmount only
}, [])
useEffect(() => {
authGetUser(usr => setUser(usr))
}, [])
const handleAuthClick = () => {
if (user) {
authSignOut()
} else {
authSignIn()
}
}
Also, here are my other relevant methods:
const authGetUser = (callback: (user: firebase.User | null) => void) => {
initFirebase()
authUnsubscribe()
userUnsubscribe = firebaseAuth.onAuthStateChanged(callback)
}
export const authUnsubscribe = () => {
if (userUnsubscribe) {
userUnsubscribe()
}
}
const authSignIn = () => {
googleAuth.signIn().then((googleUser: any) => {
var credential = firebase.auth.GoogleAuthProvider.credential(googleUser.getAuthResponse().id_token)
firebaseAuth.signInAndRetrieveDataWithCredential(credential)
})
}
const authSignOut = () => {
googleAuth
.signOut()
.then(firebaseAuth.signOut())
}
Both examples work. However, when I log out and log in with the hooks version, I get an error message in console saying
Warning: Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in the componentWillUnmount method.
which suggests that the cleanup is not done properly.
Yes, I know I could just continue using the version with the class which works. But I want to understand React hooks better by solving this.
Any ideas?

Answer 1

Wouldn't this works for you? You could use a single useEffect().
React Hooks API DOCs
useEffect(
() => {
const subscription = props.source.subscribe();
return () => {
// Clean up the subscription
setUser(null); // <--- TRY DOING SOMETHING LIKE THIS
subscription.unsubscribe();
};
},
[],
);
The clean-up function runs before the component is removed from the UI
to prevent memory leaks. Additionally, if a component renders multiple
times (as they typically do), the previous effect is cleaned up before
executing the next effect. In our example, this means a new
subscription is created on every update. To avoid firing an effect on
every update, refer to the next section.
If you want to run an effect and clean it up only once (on mount and
unmount), you can pass an empty array ([]) as a second argument. This
tells React that your effect doesn’t depend on any values from props
or state, so it never needs to re-run. This isn’t handled as a special
case — it follows directly from how the dependencies array always
works.

Answer 2

Generally, this happens when we have asynchronous requests and the component is unmounted before, occurring memory leak. Obviously, that this not occur in class-based components because we have componentDidMount() and componentWillUnmount() hooks, so it's more confident than useEffect() that we have manipulated the state, so I think that you need to identify the reason for the application unmount and there is the solution.
You should use one useEffect() instead two like this:
useEffect(() => {
authGetUser(usr => setUser(usr))
return authUnsubscribe() // runs on mount and unmount only
}, [])